Equipment

I will preface this by with the warning... don't jump into the deep end of the pool. If you have just gotten all your neat toys at once (scope, camera, mount, auto focuser, filter wheel, etc) let me give you a bit of advice. Start out with simply live viewing and become familiar with the way your mount and telescope work. This will also have the added benefit of you actually learning the sky instead of simply depending on a computer to point your scope at it.
Now, let me give you a little more advice... research HEAVILY.

The #1 rule I have learned when buying your equipment... DO NOT skimp on a mount.
My William Optics ZenithStar 103mm kit came with a rebadged SynScan EQ35-Pro. It's a decent mount for live viewing..... but once you start adding on a camera, a filter wheel, a power box and a RPi/NUC you will quickly exceed the mounts capacity.
If I had it to do again, I would have simply purchased the scope I wanted along with a flattener, and then purchased a separate mount for it that would allow for expansion.
There is probably a reason that William Optics no longer offers a kit like the ZenithStar 103MM that I purchased... as once you start doing what they advertise you can, the warts of the EQ-35 Pro fully display themself in all their glory. As you can see on the site, I'm getting some decent captures, but it takes a LOT more work than it should as I frequently have to pause the capture, rebalance and then restart the guiding and the captures.
This is an example of M31 (Andromeda Galaxy) and you can see some tracking issues present (as you can see by slight elongation of stars), and this was BEFORE I added more to my image train.


These are some more recent captures, processed using PixInSight, which I am still a neophyte with.


When it comes to telescopes, in my opinion, the easiest for doing DSO in order are:
Refractor
Reflector
Ritchey-Chretien
SCT
Dobsonian (mainly due to wonky tracking but they do GREAT for live viewing DSO objects and even getting short exposure images)

Too many people think they have to jump into a large scope for astrophotography... and the SCT/Ritchey-Chretien/Reflector seems to be the way many tend to go for some reason. With the SCT (not so much the RC scopes), you have to be careful because of certain quirks with the format of the telescope. Mirror flop can be a big issue with them. And then you usually really need to use off-axis guiding (OAG) with them, which tends to be more expensive than a guide scope/camera setup for the Reflector/Refractor telescopes.
I have a NexStar 8se that is only getting used for planetary viewing and capture right now, as the requirements for getting it up to DSO ability are more than I want to invest when I can get a decent refractor for what it would take.
My recommendation would be look at either the refractor or reflectors. For refractors, something in the 60-80mm range makes for a nice beginners scope and will get you most any target you want. You may have to do mosaics on certain ones, but there are not that many (M 31 being one).
For a reflector, I'd probably look in the 130mm-150mm range, but I have no current experience with a reflector other than a really cheap one we bought our son about 3 decades ago. I am looking at getting a GSO imaging Newtonian (relector) F4 in the 6"-8" range, but that will be a little further down the line as I really want another decent mount.

Do NOT go overboard on your camera. There are many that use (successfully) DSLR cameras. To get the best results from them, you will eventually need to mod them with filters, which tends to ruin them for everyday use. I tried at first with a Nikon D7200, and the results were simply so frustrating that I decided to get an actual astrophotography camera for use. This avenue is a good done for someone that want's to "get in cheap" and actually capture decent images. You can usually find a nicely modified Canon T3i and with a good lens, you can do wonders (but not to the level you will be able to with a dedicated telescope).

A decent intro level ASI Pro camera will do everything you generally need it to, with the understanding that if you get something like the ASI533MM/MC (which is has a 1x1 aspect ratio) you will have to learn to do the occasional mosaic (reference my M31 photo above needs to be done in one since it was captured with a 533MM Pro). But this can happen even with the cameras with a wider FOV. The benefit of most of the newer ASI cameras that you have is that you usually have NO amp glow. You really need to decide what primary targets you are looking to capture... and if you are willing to learn mosaic captures are if you have lots of money to invest in one of the newer capture cameras (like the ZWOASI2600MC/MM or ASI461MM or the ASI990MM Pro). I simply don't have $3K-15K to invest into a camera, so am more than willing to work with what I can afford.
This is a more recent capture (before I found an issue with the telescope/focuser connection) using the ASI533MM Pro.

Be SURE you have a decent guide scope and camera. For any lengthy captures, it will help greatly. Historically, the recommendation is that your guide scope be 1/3 the focal length of your primary telescope. I use a 50x200mm William Optics on the ZenithStar (710mm) and it does great. Now, for my NexStar 8se, I'm going to have to investigate further on as since it's a SC scope, it has issues with flexure and also mirror flop. I'm probably going to go with OAG (off axis guiding) on it honestly.

A decent polar scope will be of help also. Yes, with an RPi running Stellarmate or any of the Indi/EKOS stuff, you can do a polar alignment... but the closer you are when you first start, the better it is. Then that assumes that you have an adequate FOV to do a polar alignment with it having to slew to various stars. For me, using the polar scope on the mount I've been able to get decent tracking for 15-20 minute exposures since my FOV is very limited by trees surrounding the house.

One Item I'd strongly suggest if you are going to do astrophotography using something like an ASIAir Plus, a Raspberry PI 4 (8GB) running Stellarmate or Astroberry or an Intel NUC running Ekos or N.I.N.A. (Windows only). Also a nice camera rotator is HIGHLY recommended.
If you frame each of your captures for the best positioning, when you go back to it later to grab more captures using (in my example) StellarMate OS you can do a Load & Skew to the object.... and it will then tell you which way to rotate the camera to match the existing image. When you do this you have a choice of rotating the entire telescope manually, or if having installed a manual rotator simply rotating the ring, or if you are blessed with the funds to get one, the Pegasus Astro Falcon automated rotator (which I currently have and dearly love) which will do it automatically.