I posted this as a comment in another post but when I got done I realized it would probably just be better as its own post. I'm sure I could find the answers I need myself but frankly I trust the userbase here more than most online articles.
As my username hints at, I'm a lawyer. I'm considering starting my own firm as a solo practitioner. I need a computer and/or laptop for it, and as a new business my budget would be pretty tight. I've mostly only ever used windows, but I'm getting fed up with the bullshit, so I'm considering going with Linux.
I assume Linux is capable of doing everything I need, which is primarily handling word documents, viewing PDFs, watching evidence videos, and online research. But my concern is that some of the more commonly used video types might have trouble on Linux, or that some of the word document templates I use in Windows might have compatibility issues.
I'm also nervous about using an OS I'm not familiar with for business purposes right away.
So I guess I'm asking a few questions. What is a reliable yet affordable option to get started? Are my concerns based in reality or is Linux going to be able to handle everything windows does without issues? What else might I need to know to use Linux comfortably from the get go? Is it going to take a lot of time and effort to get Linux running how I need it to?
For reference, I do consider myself to be somewhat tech-savvy. I don't code or anything, but I've built my last two home computers myself and I'm not scared of general software management, I just don't make it myself.
So, yeah, sell me on Linux, please.
Others have given you some good advice but I'll still give you my opinion because more data points is good.
First of all, as others said, it's better perhaps if you switch your home computer first or try it out on a VM or dual-boot first as you learn how to use it rather than erasing Windows altogether at first. Regardless of your choice I'd recommend giving it a try still.
Affordability is not a concern at all, most Linux Distros are free and they'll work perfectly fine, usually when you pay for distros you're either paying for better tech support or to support the distro itself, and a lot of the software that's on the repos is also free.
Your biggest concern probably would be re-learning the OS. Now, obviously Linux and windows work very differently, for example installing software on Linux is mainly done via an app-store or the terminal. As for graphics, shortcuts, etc, there's two approaches here, which one is better depends on your preferences. You can either stick to something similiar to windows, so any distro that has Cinnamon, KDE plasma, or Xfce (you will have to move a few stuff and configure it a bit at the beginning) will do well, I'd recommend Linux Mint; or you can do something more different that will force you to learn something new and will tell you visually "Look, I'm not windows, I'm built different!" so something like GNOME (or customize the other DEs to something you like), personally I'm not a fan of GNOME but it works well for your use-case, as any DE will do, in this case I recommend Pop!_OS.
Both of my recommendetions use apt and are debian (through Ubuntu as the middledistro) derivatives btw. This is important because when you encounter a problem or a certain software not being in the repo it is good to look for sources closely related to your distro.
Linux can do everything you mentioned and more, however compatibility with M$ Word documents/etc can be a bit iffy. Personally I always used LibreOffice and aside from some minor annoyances never had issues with it and using .docx but I also don't work at a professional environment that requires it to work perfectly. However you're in luck as you can still use M$ office & other stuff from your browser if needed, tho I assume it will have less resources and will require an internet connection (this can be mitigated by working offline with LibreOffice, OpenOffice or any Office suite you like then copy-pasting it to M$ word or whatever), tho I wouldn't know since I don't use either and never planning on doing so. There's also google docs.
Video types should work just fine especially common ones, VLC is a powerful tool. If you're installing Mint make sure to install the media codecs at install.
Also I recommend learning the terminal, it may seem scary at first but it is easy, fast and will help you troubleshoot. Also accept that you will encounter problem, like in every system, and you're expected to solve them yourself, this means you can spend a lot of time looking up stuff, learning to look at logs, etc. This will of course take time but it would take as much if not more time on windows too sometimes, on the bright side Linux tends to be a little better at telling you the problem if you know what to look for and also you almost never have to deal with an issue until the company fixes it, you can literally go and fix the code yourself if needs be. Anyways, on this end I recommend using a stable distribution (like the ones I mentioned), stick to the official repos as much as possible, and at install make a separate partition for your home folder, that way worst case scenario you can always just reinstall the OS (takes 15 mins) without losing your files*. Also, this goes for everything and I can't stress it enough: MAKE FREQUENT BACKUPS, and better yet do them in multiple places: Proton Drive, external hard disk/USB, an other drive on your PC, whatever just have at least one, preferably 2+, place that isn't your computer or its main drive be your backup space. This goes for Windows too and even though I assume you know it I will still say it because it's extremely important and always overlooked.
*Unless you erase the partition by mistake or something.
P.S. also given the nature of your job, you might want to encrypt the hard disk (write the password somewhere and make sure to use a password specifically for it and one you can remember, password managers/generators don't help here) and learn to use the gpg command when you need to encrypt and sign documents.