I’m planning to upgrade my internet to a gigabit connection soon, and I started thinking: Since my router is connected to a (managed) switch with a 1Gbe link it will become a bottleneck between devices connected to WiFi (on the router) and ones connected via wire (to the switch). Can I (and should I?) consider connecting my router to the switch with 2*1Gbe links and using link aggregation and/or spanning tree protocol (to prevent loops)? If so, how should I configure it? My router (r7800) is rather powerful and should be able to handle it.
Which router, it matters a lot - as many contemporary routers don't even have the bandwidth between their switch and the SOC (so bonding might not even help).
If you can pull two cables between your switch and the router, it probably makes more sense to dedicate one cable as uplink cable to the modem/ ONT, and a second as downlink towards your switch (avoiding link aggregation, keeping them separate). While you are right that the aggregated throughput of multiple LAN networks and wireless might exceed 1 GBit/s, it's rather questionable if you can notice it (in practice not with 802.11ac, but 802.11ax can push you beyond that - however how much of that you will really 'feel' (with interference at play and beyond the immediate vicinity of the AP) is another question). At some point 5GBASE-T or 10GBASE-T might be the natural progression, easier to implement (both software and considering the 'typical' hardware for routers and their bottlenecks).
My router is Netgear R7800
Not sure what you mean about the uplink - I'm connected to the internet via my routers WAN port with RJ45 cable, no other router/modem involved, but if I'm going to need one it is still going to.go there.
So what I want is 2 connections between the router and switch so the internet can't saturate the whole link between devices connected to the switch (wired) and ones connected to the router (wireless).
Since my (managed) switch (https://amzn.to/3pnt7Qy) has 4x1Gbe, 2x2,5Gbe, 2x5Gbe and 2x10Gbe ports I am probably going to switch to a router that supports 2,5Gbe or higher eventually, but I'd imagine that even if there are routers that support this now, they'd be rather expensive.