Congrats on the amp. There are quite a few of us on here who use the Boss Katana.

If you do a search on it you'll find a few threads. I wouldn't focus too much on figuring out all the tones. Let that all come to you as you learn. I usually just keep mine on the clean setting or acoustic if I'm playing that and yes .5 watt is enough for me, plus I have 4 preset settings that I downloaded from a patch site. Thats really the best way to get the sound you want is to download the patch from Boss website or you can find some public domain sites out there that have some custom ones. The directions are pretty intuitive on how to download and install them. And of course some of the more experienced players on here can help with any questions. I'm still a bit of a novice myself when it comes to all those tones.

Have fun,

Moe