By default, OpenBSD uses FFS / FFS2. There is an effort in place to port GeFS (from 9front) to OpenBSD. It's unlikely that ZFS will be ported to OpenBSD, due to licensing incompatibilities. For the same reason, btrfs is also unlikely. That's why I run FreeBSD on my big server, and OpenBSD on my laptop and other edge devices. I don't really have any issues running FFS on a laptop; it seems overkill to run anything more advanced than that.

I'd recommend taking a look on forums to see what other folks are running. If it's a modern Lenovo with integrated graphics or an AMD GPU, it will be supported before others. OpenBSD folks tend to use Lenovos. My best recommendation is to pick a laptop that a core maintainer is using, unless you feel comfortable making your own patches. They have AMD GPU support via DRM from Linux. Intel graphics typically works alright.

OpenBSD works well with relatively recent versions of Chromium and Firefox. That being said, they are on a six month release cycle. The Chromium port can fall behind if you stick to -stable or releases. Building Chromium or Firefox from source is... well, I have a 2012 laptop, so that's not something I am going to do. Regardless, you'd need to be pretty comfortable with applying OpenBSD specific patches to one of these browsers, which isn't always obvious, especially since they are moving targets.

If you're used to being on a rolling release Linux, this will be a bit disorienting. But, in my opinion, it's significantly more stable and better thought out.