I have two old netbooks with the same CPU as yours, but with 1 Gb of memory instead of two. They both run FreeBSD and it works very well for many things, but not for a heavyweight web browser playing YT videos. For a window manager, I strongly recommend Openbox first. It only takes up only 150-200 Mb of RAM, depending on what extra you use. With some keybindings. Openbox is really nice and lightweight. If you want a somewhat fancier "almost desktop" window manager, I would recommend IceWM. They both make my old machines alive. You can also use XFCE, which is a fully-fledged desktop, takes up only ~350 Mb of RAM in 32-bit (which is impressively lightweight for a desktop), and it works - but it is noticeably slower in such old machines.
I doubt your extra Gb of RAM will make much of a difference as far YT video playing is concerned, because web browsers became really resource demanding - and those that are lightweight won't play YT videos. Still, if you insist using a web browser for YT video, try Invidious instead of YT (because YT itself is really heavy with all the spyware it has built-in).
It is worth trying other solutions, avoiding a heavyweight web browser. Your best bet is
gtk-youtube-viewer
or even command-line tools like
ytfzf
or
yt-dlp
.
All the above mentioned applications are available in FreeBSD 14, 32-bit. The problem is 32-bit is going to be dropped in FreeBSD 15, meaning sooner or later we will have to look for other solutions in such old machines. In that case I would recommend trying
Haiku or
antiX GNU/Linux.