Brume is the most powerful GL router at the moment, so it will give the best VPN performance, and has the fastest CPU. The idea is that you place it as an edge router, the closest device to the internet, handling your entire network, with a wireless access point connected to it since it doesn’t have wifi (1000W does have, but only 2.4ghz).
It’s possible to flash Ubuntu on the Brume as well.
The linksys router has AC wifi, so it will be better if you need wifi, while Brume is better because of the easy to use GL UI, letting you configure Wireguard, OpenVPN and most settings you will need, without the large learning curve of Vanilla OpenWRT (you need to configure everything manually).
Yes SSH is available out of the box, user root + the password you enter the first time when you log into the router, and there are threads here how to harden that security as well:
Flashing Vanilla OpenWRT, it should be possible @alzhao can comment.