I have two big questions...
When was the last time you reloaded it and what CPU you have.
By 2 years Windows is crying for help in almost all instances. Yes, Win10/11 does better on that front than Windows past but they still need a refresh now and then. And frankly I suspect Win11 is actually a regression on that front.
Everyone points towards memory with browsers but the cpu is VERY, VERY much also a bottleneck. not just speed, but also cores, unfortunately adding more cores is not necessarily going to make it better as browsers aren't really written to capitalize on a ton of them. One thing is for certain about CPUs though is that Windows HATES I3s. Something about how Intel manages the power cycle on them, they just feel laggy, no matter how many cores, or the frequency. If you are using an I3, that's part of the problem though it can be minimized by going into power settings and upping the minimum cpu. It will eat a teensy bit more battery but make things peppier. Memory is there to be used, no matter how much you give it, it will soak it up, and not always in the most efficient way.
Not having enough CPU will make you think ram is a problem but having too much ram is rarely a bad thing, I would rather an I5 with 8 gigs ram than an I3 with 16gigs of ram. That said, an I7 is barely any faster than an I5 (just look at the frequencies ) so an I5 with 16gigs is going to be a better computer (in general) than an I7 with 8gigs. An I 7 is often rarely worth the price increase and I pretty much only setup up when you get more cores or a special feature like hyperthreading or virtualization. The frequency bump alone isn't worth the price, that goes double when buying new.
Another thing you may be running into is the USB to display.
USB has overhead, and running screens can be pretty data intensive, and just memory and cpu, you can flood the chipset when doings so. The latter is a bit tough to diagnose as the cpu and ram may not really indicate an issue. It's also very much an issue for Igpus, they just really don't do well with that many screens. You're effectively using 3 displays and most IGPUs aren't even designed for more than two external, some will not even allow more than two, though you can force it with a USB adapter... but again, there goes your I/O. "But it's Thunderbolt..." That doesn't mean as much as you think and depending on implementation may be sucking down a lot of more resources than you realize.
As for 32gigs being enough...
Frankly other than some specialty software there's little out there really able to use 64 gigs, nor will there be anytime soon. That goes double when coupled with a low power laptop CPU like a Surface is going to have. Sure the browser will suck down all 64 gigs, but the system will be dog slow long before you even break 32gigs because the cpu (or something else) is going to be run ragged. My point being everything matters and while you might fix the ram problem something else may be lurking right behind it so you could spend a lot of money and only see a very, very minimal improvement.
I'm not sure exactly what is bottlenecking you currently (probably ram and cpu) but I'm pretty sure your replacement options will suffer a similar fate, just maybe just a little better and if not now, it will soon enough. You may not want to hear this and you may have already figured it out, but you really should consider a gaming laptop or a desktop pc with a low end GPU and some dedicated graphics ports because you are not the typical use case. You need more GPU, you need more CPU, you need dedicated I/O, not just more ram. That said, there are very thin and light gaming laptops and there are gaming desktops that are to be frank, TINY. Mine's the size of a toaster, but I could easily cut that in half (or more, think Mac Studio or smaller) for what you need and can easily be tossed into a carry-on. There's even smaller ones with AMD chips with IGPU's that could work for you, think Mac Mini or even smaller, look at Beelink GTR7 as an example.
