For example, but is not all:
...and prefer using some cheap Tenda...
Than sometime enable DHCP server on itself for no reason, also if apparently correct installed...
Removed ether2 from the bridge
What bridge? If the user (than till now has not replied about) has old RouterOS with master and slave interface, do not have any bridge...
...Also if prior to RouterOS7 ...
Please do not suggest beta to new or inexperienced users....
set the local network dhcp server (192.168.88.0/24) to ether3
the IP, if any from default configuration, are or on bridge, or on ether2-master: or is leaved on bridge, where must be, or be set to ether3 after make ether3 the master and 4 and 5 the slaves.
It wont let you remove ether2 or just freeze the network
What mean?
Removing / moving IP cause lost connection if the device are managed by IP, do not freeze the network
For cleaning purpouses I renamed ether1 and ether2 to wan1, wan2.
Better to leave the default name and instead enter WANx in the comment, which is then visible in the drop-down menu,
or at least call it as ether1-wan1
Then added a DHCP client on the wan2 interface.
You just forget to suggest to use different default route distance,
if the distance are identical, the connection with little IP value are choiced for connection.
For use both must be done, as you say, routing, pcc, ecmp, etc.
Simply set the default route distance, for example on the line with most performance set on DHCP client the default route distance 10, and 20 on the other.
If the main connection stop working must be used some form of failover between two wan, before do any traffic shaping, PCC, etc.
Because if stop working, or you detach the ether cable, or probably the router until dhcp client is active do not understand that.