Andy, welcome to this learning platform!! So glad yo hear that you're learning a lot already! I'm always available here if you want to ask me (or any of the other guitarists here at the forum) any questions! :)
Really cool that you want to start writing out your own arrangements! For me, being able to write them out, and then "save" them is something that I've put a lot of effort into over the years, and it's actually a special feeling to see your music on the paper. :)
I started off using Sibelius, and I liked that software for music notation. However, even though I had bought the software (for around $600 way back), Avid (who owns Sibelius) started charging an expensive monthly fee even though I had already payed for the software. This made me (and many many others) switch from Sibelius to Dorico. I now use Dorico 5, and I really like the software - although it took me a couple of months to really get used to it after using Sibelius for years..
I should mention that I write out my arrangements using music notation (I do read notation even though I'm a guitarist, haha), and then I transfer the music notation to the TAB staff, and adjust what notes are played on what strings after that. I mention this because I think there are softwares that might be easier to use if you're writing TABs before the notation - but I'm not sure which ones are the best for that.
Let me know if you have any questions!!
Kind regards/Emil