Is a dog crate OK for my hedgy?

With a CHE and a lightsource, and covering the bars, there isn't an issue. Dog crates seem small to me, but then again, the ZZ2 seems tiny. What is the square footage of the crate? The ZZ2 is 5.5 square foot for comparison.

One thing I noticed is that you're using a bottle. You should really be using a bowl for water, not a bottle. The bottles are for rodents, who have a vertical posture and constantly growing teeth. Hogs are horizontal, so bottles are at the wrong posture, and they aren't rodents (or rabbits), so they don't have the constantly growing teeth - hogs have chipped and broken off teeth on bottles, which will involve vets visits and irreplacable damage. They've also been known to catch hog tongues, and there have been hogs with bleeding tongues where they've struggled to free themselves :(

Think my perspex is 30 cm high. Bodhi can stretch out 20cm easily at full reach. 30cm is what is recommended (or at least, the inch equivalent) on the US forums to ensure there is no stretching, even of the largest of hogs. Also helps keep some of the heat in (probably not) and definitely stops draughts as obviously this is on the floor.

TBH, the whole playpen thing makes me laugh. People want to put their hog in a playpen during their 'nighttime'. Who among us humans would like to be woken at 3 in the morning, kicked out of our nice warm bed and told to go for a 3 mile jog, and then, when we get home, are given instructions to play monopoly for the next hour. Pfft to that! A bigger cage is more useful to a hog - they do the majority of their activity, exercise, running, playing and exploring during the night - the bigger the space, the better. If you know the measurements of the cage, convert them to feet (typing 'convert <cm number>cm to feet' into google works admirably!), and then times the length by the width (ignore the height) - gives you the square footage. 4 square foot is absolute minimum, ZZ2 is 5.5, and for reference, Bodhi is in 18 square feet. The higher the square foot number, the better. If you can get 10 with the dog crate, then I see no issue with that - double the ZZ2 size makes it very much worth the expense. They will make use of the bigger size.

Age has no relevants with regards to animal husbandry. Don't care if the hog is 2 days or 18 years (HA!), the proper equipment should be attempted. It is probably far more stressful for a hog to have to struggle to get water, than to offer a bowl as well. Most people suggest placing the bowl under the spout of the bottle to encourage use. Then placing the spout in the bowl, and then just the bowl. Your vet is talking tripe. If it was the other way around, and you were doing something that might degatively affect the hog in some way, perhaps - but you are already changing the cage, the bottle to bowl is minor to that. Be a bit like saying you were 'stressing' a 60 year old out by feeding them fresh fruit and veg if they'd only ever had canned stuff. Might be novel and take a while for them to realise how much tastier it is, but the fringe benefits to health far far outweigh any hesitance to inspect a novel object.

I use a cat bowl which is about 14cm wide. I got one from the US, and Joey (on here) sells them in a variety of colours with polka dots on them, so I have two of them as well. You want them to be quite shallow though, so I'd think rabbit ones might be too deep. Hogs won't be climbing onto the side, after all. Bodhi's US one, she walks through (which isn't practical!). A lot of people use normal bowls though, and I've used Gu Puds ramekin bowls during wash day - they are fab!

Smoothing quills, if Bodhi ever glares at me if I wake her up, or someone surprises her (more likely the latter, thankfully!), I stroke her quite firmly from shoulders to bum. This works for unballed hogs, but you have to be quite firm about it - although obviously not hard enough to hurt. Technique I got from my breeder, and it definitely works with normally placid hogs.