Don't do that. A host shouldn't have multiple IPs assigned to the same subnet. This will screw up routing. So either use 192.168.88.88/24, 192.168.88.99/24 or 192.168.88.89/24 but only one of them. In your case you probably want to use DHCP on wlx18a6f70bc768 for the 192.168.88.0/24 subnet and some other subnet for vmbr0.
Sorry but maybe I do not get the idea how it works.
I thought that the main server IP, for example for web access, should be the WiFi interface (wlx18a6f70bc768) IP address (192.168.88.89). If I use DHCP on that then I get web access on random IP address and everything becomes a bit complicated. Am I thinking the wrong way?
What subnet should I use for Bridge (vmbr0)? Does it have any restrictions instead of not being in the WiFi interface (wlx18a6f70bc768) network?
I've got 3 IPs on the server - Ethernet, WiFi and Bridge, should I transfer the Ethernet IP to another 3rd network if I even wanna use it?
Also should router be in the fourth network or is it OK for WiFi IP interface to be router subnet (192.168.88.0/24)?
Thank you for your help with goofy questions.