For my book projects (mine aren't Tapas related but this program could still be useful), I use Reedsy, which is a free website that allows you to write directly online, and it lets you format your book 'professionally' with sections, chapters, quotes, front and back matter, etc etc, all that as you go. You can move things around really easily and it's just so smooth to use. Another great thing on Reedsy for people considering any kind of publishing is the Marketplace feature, which allows you to contact and hire publishers and editors with lots of credits and experience in reputable magazines or publishing companies. For corrections, I leave it all to good old Grammarly.
To make my comic, I currently just use Ibispaint X on iPad since it's free and pretty much made exactly for comic creation. It's honestly amazing for a free app, tons of features, it allowed me to start a project I'd been dreaming about for so long and without spending any money. The only downside is watching 30s ads to unlock all the brushes every 18h (quite worth it if you ask me), though I guess the sheer amount of stuff packed in the app is kind of another one, since it overheats my iPad quite fast and I usually sit down for 6-8 hours of drawing. For poses/any other references or even just inspo, Pinterest is my go-to and more often than not, a lifesaver. If all else fails, I'll take pictures of my own hands/mimic poses in the mirror lol
I recently purchased a 2-in-1 touchscreen PC, and I'm honestly very sad to leave Ibispaint behind! I'll be switching to drawing on my laptop with Sketchbook; the full version is now free for everyone and from the little I've tested it, it seems pretty good. Someone mentionned Gimp and I've been using it for graphic design for years, but I'm not sure how good it could be for drawing and making my comic... Guess I'll have to test that out too!