I havent upgraded my PC in over 7 years and it's getting to the point where I may need to look at spending some money on a new one. First question is, what are the latest wireless mice like? Years ago there used to be a lot of input lag which when working and playing pushed me to a wired version. Are the latest generation of wireless mice any good?
Difficult one, I've two wireless mice that are OK - RAT 9 and Steelseries WOW mouse. Most others I've tried though have had the usual laggy, inaccurateness you probably remember. I suspect that the dearer ones are OK, but budget ones just don't have the better parts. Somebody will probably chime in about logitech offerings, they're often well regarded. Certainly if you don't mind a wire, that way is easier and cheaper to get good performance from/
I use a Logitech MX Master at work and its perfectly fine, but of course you can get multiple decent wired mice for the price of one of them.
I picked up a G700S on offer and I like it as it has more buttons which I find useful than my G5 but the battery life is awful, hence the reason I have it permanently plugged in to my Keyboards USB hub. Wish the battery life was better though, the cable does cause issues once in a while.
I've got the same mouse as you, with the standard battery that it came with I found the same as you. I put a higher rated battery in it and found that the battery lasts a few days more between charges than it did with the standard battery.