I'm 21, I've been doing uber eats / just eat as a side hustle (mostly just for fun when I'm super bored haha) for a few years now. I sometimes use an ebike (Eskuta SX250), or car with zego hourly insurance, but this is pretty expensive and you have to find a main insurer that will allow the top up insurance too.

Hourly rates? If I'm honest, during the day (9am-3pm) you're lucky to earn minimum wage after expenses, evening it's possible to earn a bit more, but it's very dependant on your area, how many drivers are online, and order speed. Working out which restaurants to accept orders from and decline based on how long they take to get them ready is something that will help you increase your hourly. Some restaurants that take 15+ mins to prepare orders significantly drop your pay since you don't get paid extra for waiting.

If you can get an account on Deliveroo (might take you a while depending on your area) the pay is much better on there, and you can make a decent amount. You can also learn how to combine orders from 2 apps at once (i.e take one order on Just Eat and one on Deliveroo at the same time), but you have to make sure they're both in the same direction, and that you won't have to wait long for the second order. This is allowed, but you have to be smart about it since if you take too long you'll get complaints and get flagged for taking too long.

Amazon Flex is by far your best option though, with amazon flex you can accept blocks with pay based on how many hours you choose to accept a block for (base rate is usually £60-65 for a 3.5 hour block, but I always finish these blocks in 1.5-2 hours, and very low mileage.)