The temperatures sound normal though case airflow really changes PCB backside temps a lot while chip temps may stay roughly the same. This really depends on your case and fan setup.

The VSA-100 chip was designed to run on lower voltages but yields were too low so 3Dfx gave them a little more juice and they run a bit warmer than anticipated. Afaik there's a later stepping of that chip that is fine with passive cooling.

You can look between the chip and the cooler from the side. If the cooler sits more or less flat on the plastic of the chip it should be fine.
If there's a huge gap you may want to remove the cooler, remove the thermal glue and glue the cooler or an aftermarket part back on. With aftermarket coolers you may be able to use thermal paste and the mounting holes in the PCB.

Be careful when removing the stock coolers. Usually your best chance is prying between the heatsink and the plastic of the chip. Do not pry against the chip's substrate or the card's PCB.

The temperature measurements were taken with an IR gun with one side-panel removed from the case. It's a reasonably modern case layout with a lot of mesh panels for airflow and there's currently one 120mm intake fan mounted bottom-front and another mounted top-rear for exhaust, but they're both quiet low-RPM fans so the actual airflow isn't likely any more than you'd have with two higher-RPM 80mm fans. The PSU also has an exhaust fan, sitting bottom-rear. A large portion of the top of the case is mesh and there are mounts for two more 120mm fans, if required.

As for spacing between the chips and their coolers, I'd say each one is flush at its best corner and maybe 0.5mm spacing at its worst corner. I doubt the thermal transfer capability of this glue is nearly as good as modern thermal paste, so 0.5mm could potentially be a lot. I'd prefer to keep the card looking stock if possible but I'm not necessarily against a pair of aftermarket coolers IF I can find something that looks visually similar and uses the mounting holes on the PCB rather than this glue nonsense... plus it would be neat to feel like I had the headroom to overclock without feeling terribly guilty about it.

Any specific models I should search for in terms of aftermarket coolers, that look similar to the stock coolers but use the PCB mounting holes? ... oh, and the fans would need to be 5V fans I can adapt to the fan headers on the card itself, even if I had to do some wire splicing. There's something I find very unprofessional about a VGA cooling mod where the fans have to plug into separate power.

AngieAndretti wrote:

As for spacing between the chips and their coolers, I'd say each one is flush at its best corner and maybe 0.5mm spacing at its worst corner.

For 3Dfx/STB standards that's actually pretty good. 😉

AngieAndretti wrote:

I doubt the thermal transfer capability of this glue is nearly as good as modern thermal paste, so 0.5mm could potentially be a lot.

That glue is relatively bad compared to modern thermal paste but keep in mind that's a pretty small gap to be bridged and the chips don't dissipate nearly as much heat as modern GPUs and your case is ventilated a lot better than what was to be expected in 2000. You're probably fine with your card the way it is right now. 😀 Also there's always a risk involved with removing the coolers.

AngieAndretti wrote:

Any specific models I should search for in terms of aftermarket coolers, that look similar to the stock coolers but use the PCB mounting holes? ... oh, and the fans would need to be 5V fans I can adapt to the fan headers on the card itself, even if I had to do some wire splicing. There's something I find very unprofessional about a VGA cooling mod where the fans have to plug into separate power.

As much as I'd like to I can't recommend a certain model to just work out of the box because those old chipset coolers are not always avaliable in new condition and I don't know any that fit the Voodoo 5's PCB hole spacing without modifications.
Also with the original 40*40mm size the only way of improving the heatsink would be to go thicker. Same goes for the fans - the original ones are pretty thin and I don't know any good black 5V 40mm fans.
The Titan TTC-CSC03E might do the trick with a little filing in the mounting holes and it looks similar to the stock cooler. It also appears NOS from time to time on Ebay. The heatsink itself won't perform much different from the stock heatsinks but thanks to the push pin mounting you can use thermal paste. The fans run at 12V though. I doubt they'll spin up at 5V.
Keeping the look and increasing cooling performance is hard.

For overclocking you're likely limited by the VRAM chips anyway. 😁