

This laptop is more than capable of running SNES emulation; its 1GHz quadcore, and 4gb ram.
SNES is an old system which had 3.58Mhz CPU and 128kb ram; you’ll be able to emulate it without much issue on that laptop. BSNES has low requirements (like an Athlon or Pentium 4, and 512mb ram, and Open GL2), although if you have problems then Snes9x and ZSnes are less accurate but lighter weight. RetroArch is pretty convenient way to deploy emulators and has BSNES, Snes9x and Snex9x_Next cores to use.
A lightweight Desktop Environement may help make the laptop feel snappier; Xfce or Lxqt. If it feels slow then you want a minimal desktop which doesn’t have overhead like compositing. Also don’t use flatpaks especially if you multitask; use native apps as flatpaks have some overhead.
Mint as a distro is fine for installing lightweight desktop environments, and if you wanted you could install Linux Mint Xfce edition from scratch.
How small is your smallest device? BTRFS doesn’t have a minimum size, but practically probably 50-100mb is just about doable before even just setting things up get complex. Having said that though, it’s copy-on-write and has overhead as a result, so may not function well below 1gb.
ZFS meanwhile really won’t work well below probably 8gb. It’s also copy-on-write but with a lot more overhead due to how it works. It really works best on big drives and filesystems.
If your old storage is in the mb range, then really neither will help you achieve what you want.
BTRFS and ZFS do offer the same benefits as NTFS with regard to compression and speeding up some slower devices (due to lowering the actual read/writes needed to achieve the same result as the data is compressed into a smaller space and decompressed rapidly by the PC in memory), but NTFS can go be used on much smaller disk sizes due to how it works. BTRFS and ZFS are designed and optimised with other benefits in mind. And NTFS compression isn’t well supported in Linux.