I connect to the internet using a fibre modem with a DHCP-server. Behind that there’s a switch and several access points around the house.
Since I’d like to access contact outside my country I regularly use VPN on my pc.
I would however like to add VPN to other devices too like my PS4 and TV.
Will one of the routers presented here work for this task?
Should I buy a high-end router like the GL-AR300m and could I simply use OpenVPN with a subscribed VPN service like Cyberghost or VPNExpress to gain access?
All of the devices offered by GLi will have the same technical capabilities relative to OpenVPN as they run basically the same software. There are differences between the units in terns of CPU, flash, ram and other capabilities (GPIO for example). OpenVPN is resource intensive, so the GL-AR300M will likely give you the best performance.
OpenVPN may substantially impact your speed. You can probably be happy for video with 7Mbps or more, not sure how fast you need for games, though latency will probably be more of a factor. You have not stated how fast your fiber is.
I can generally attain the required speed on my AR150 when my connection is fast enough, and yours is a lot faster than mine. Still, horsepower is your friend (for encryption), so the AR300M is probably the best choice in GLi. Also check the speeds offered by the services.
Unclear if running a router behind a router will offer you any pass through\firewall issues.
When you get some time, can you please post some speed tests with and without VPN. Also please let us know what VPN your are using and what country(S).