When I play online, I always use Emmet Byrne's custom class sheets. They are more clean and detailed than the official ones: skills are grouped per corresponding ability, and class and subclass features get each their own box to fill so that everything is tidy and very easy to read. You can take a look at the sheets at this Imgur link, and download them on DM's Guild (while the suggested price is a few dollars, you can pay what you want, including $0).
When I play irl, I use Pravelli's pocket character sheet. I have a very small handwriting, so the small writing space doesn't bother me, and the size of the sheet allows me to put it in my pocket or my wallet, which is very handy indeed. You can take a look at this Imgur link, read the instructions here, and then download it on DM's Guild (THIS is the link to the character sheet, and THIS to the matching spellbook). Again, the suggested price is a few dollars, but you can download it for free if you don't want to pay. Feel free to donate a few dollars out of your pocket if you want to reward the creators' efforts.