There is no simple answer, and possibly you're looking at costly equipment costing many hundreds of pounds. Depends on
- speeds you want to see?
- your specific need 1 Gbps in the first place?
- what property size and construction type?
- what your budget is?
- how many devices and what types you're connecting?
- any "special uses" such as very large file transfers or continuous connectivity needs?
- how technically inclined you are?
- If a large or challenging property, is it an option to run ethernet cables to distributed access points or mesh units?
- and crucially what the Hub 4 is currently NOT doing that you would like it to?
As example issues: A Wifi 6 router or mesh will have higher speed potential than an 802.11ac router, but only delivers that if you have Wifi 6 capable devices; By running the hub in modem mode you'll already be losing 15% of the hub's speed potential because it is constrained by 1 Gbps ethernet ports; If you're techy enough you can "shotgun" the ethernet ports to bypass this, but you need to be a bit obsessive to get that far; A single standalone router might be fine in a favourable wifi environment, but could struggle in larger properties or unfavourable wifi environments; Setting up access points will usually deliver faster speeds than a mesh system, but requires ethernet cabling between the router and the access points which may be anything but simple; All very well taking advice from people here, some of whom who have a very advanced grasp of technology, but whose needs differ from your own - who will actually be configuring and maintaining the wifi setup? Are you comfortable with the rather more complicated situation if there's a broadband fault, and it is down to you to establish where a fault lies and get VM's ineffectual customer services to resolve the problem without blaming your equipment? Specs aren't everything, if you want the most capable kit you need to stick to premium makes (Netgear and Asus would be in mind).
By supplying hubs (which integrate a modem and a wifi router) all ISPs create the illusion that wifi is a simple appliance. It can be, and my mid-low end mesh certainly is, but for those pushing the envelope of performance needs, either in speed, range, network complexity, device numbers you have to understand your own needs, what your priorities are, what the differences and capabilities and tradeoffs are of the various possible "solution architectures", the capabilities of different equipment.
Answer the questions above and those who wish to help will better understand what you want and the recommendations might become more suitable. Apologies if this seems to be complicating things, but that's the reality if you want to "do justice" to a Gig 1 connection using primarily wifi.