I have a Huawei router "Internet with legs" on Three. I've not had as many tabs open as you've mentioned previously but I've had six open and some online live auctions which it coped with OK.

If people remember, when Openreach messed up my connection last year, I was without net access for a month so that's when I used it.

Just recently, my "proper" router died.... so for a few days (until a new one arrived) I was using the above again with a PAYG SIM card.