I would agree that MIPS can be a good feature to have in a high speed ebike application, and many if not most of the best rated helmets happen to be MIPS helmets. Another factor to consider is whether you want EPS (One hit) or EPP (Multi-hit) foam. For street riding, EPS is fine as you don't expect to tumble and can replace it after a big bail. If you plan to ride off-road a lot, or certainly if you are interested in a little light downhill, EPP may be worth the money. It is designed to take many small tumbles without losing it's protection capacity, although if you are riding that hard you probably want to replace it every season or so anyway (and still after any major impacts). EPP helmets are becoming the norm for alpine skiing, because skiing is just repeatedly falling downhill and if you aren't bailing, you're not trying hard enough. lol
As for chin protection, it sure is a good idea if you plan to ride fast all the time, and some helmets have removeable chin guards if you are interested in that, but most don't ride on the street with chin protection as it's hot and heavy. At the end of the day, you just have to ask yourself how risk adverse you are. Some motorcycle riders will only wear the best SNELL full face helmets, and some are happy with salad bowl Harley specials.
I have three Bicycle helmets. One full-face Giro DH helmet for off-road, a Thousands Heritage for town riding, and a super light Bell EPS for backup/summer and guest use. The Giro is non-adjustable, non-vented, has full chin and ear coverage, double shell for exceptional puncture protection, and fits me just right ( I just wash the liner after a haircut and it fills in the difference nicely). But I can't add a beanie for the cold weather, and it's hot in the summer if you aren't moving fast. The Thousands fits quite well, and has enough adjustability that I can add a liner for cold days and adjust for best comfort between haircuts (I have very thick hair so it's a thing, lol). It has minimal venting, but that really helps keep me dry here on the Wet Coast, and provides basic puncture protection if you end up in the bushes along the ditch. It also looks the most casual and fashionable if that matters at all (it shouldn't, but hey....) The Bell is a super light skeletonized EPS with basic adjustability and a removeable visor. It is solely for super hot summer weather town cruising as it allows the most air flow by far, but the least puncture protection.
There is no magic all-in-one, so you have to make those riding style choices and decide where you fall on the risk/comfort/style spectrum. Whatever you do, don't buy anything off Ebay/Amazon/Ali-express if you don't know the name, can't guarantee it's legit (not a cheap clone), and can't thoroughly research the reputation. I've seen cheapo knock-off helmets split clean in half during a big fall.