Replacing carpet in converted garage office / closing wall vents

Renovating, removed old carpet, what to cover subfloor with instead? The room is dual use (office / sofa+TV) and gets colder in winter. It might become a home gym in the future.

Looking for a budget and easy DIY option, avoid cutting planks ideally, easy to keep clean with a robot vacuum.

Leaning towards roll vinyl so I don't have to use protective sheet under the office chair like with carpet + some nice rug in sofa area. Concerned it will be much colder in winter.

I also like low profile office carpet tiles (they are used in some gyms too), as I understand those are glued directly to subfloor so also losing insulation from missing underlay.

Also can the underdoor vents(?) on the picture be blocked somehow, spiders keep getting in there and it must contribute a lot to the coldness of the room?

Thanks

Look at adding insulation under the floor.
Vents are there for a reason so investigate. You don't want dry rot or condensation.
Skillbuilder channel on YouTube covered this.

As for flooring whatever. Carpet tiles are good and easy to fit.
Plenty of cheap carpet that will last a few years

Flooring has almost zero effect on temp of room .