You can send to bc1 address any controlled amount which doesn't exceed 21 000 000 of
BTC but probably it's not good idea to hold on such kind of addresses the big sum due to their
length-extension mutation weakness.. bech32 addresses are panned to be updated to bech32m
You are confused about what this means.
First of all this doesn't affect the version 0 of bech32 addresses due to their length limit (20 and 32 bytes only) which is what we are using right now since there is no version 1+ yet added to the protocol. And when the newer versions come they will use the new format while v0 can stick to the same old format without any issue.
Secondly even for vulnerable version 1+ this mostly affects you when trying to transfer the address over an insecure channel that may be maliciously changed. In which case you have more things to worry about than this vulnerability.