Would they not supply you with a router?
They don't supply one as standard, so if you want one from them, you have to pay for it. (That's one reason why they can offer a 12 month contract and no setup fee)
Aquiss seem to recommend specific models of TP-Link router:
https://support.aquiss.net/en/knowledgebase/article/...
At least if you have a problem with any of these, Aquiss may be able to help you fix it.
If you want to choose something else, then it depends what sort of features you're looking for. I have Mikrotik with separate Ubiquiti wireless access points, but I'm hard-core techie
Most modern routers should be able to handle a gigabit FTTP connection (900/110). Some people have said that the Ubiquiti Dream Machine doesn't work very well with PPPoE though.