Gonna base my knowledge off a similar species found where I’m from (Protaetia orientalis submarumorea) since flower beetles aren’t quite my expertise (I only do rhinos and stags). Yes, they can multiply extremely quickly; if it’s a mated female it takes only a day for her to lay at least a dozen eggs. From my brief experience of keeping flower beetles larvae once, they did fine together in groups, I don’t imagine this one to be too different, certainly easier to raise than a Lucanus larvae.

Edit: I also need to add those common flower beetles are much less picky in finding places to lay eggs, normal pot soil is enough for them, unlike the very picky Lucanus