Hi Pillar!!
I just built in a Phanteks P360A (smaller version of P400/P500), literally like 1 hr ago.
Highly recommend. Build quality is great for a $70 case, comes with 2 DRGB fans (good at this price), and has mesh option if you care about performance. I think the non-mesh versions have a largerish opening at the bottom to let air in, so might be better to get the mesh anyways.
I don't think there are any holes for ingress larger than like ~1-5mm (exhaust outlet has ~5mm hole grate like most cases). They seem to have blocked off most entry points in order to get the air to flow correctly thru the designated areas, which would also have the effect of not allowing moderate sized bugs in.
Hopefully you can solve the bug problem!
edit: for non-Phanteks options, I cross shopped the Corsair 4000D, and was going to purchase but it sold out while I was debating so I went with the P360A instead. The 4000D Airflow version is a good performer, and I believe the front intake has a filter that should keep bugs away. Otherwise they have a non-airflow version, but thermals are probably significantly worse.