squid itself is not installed in Proxmoy by default. If you installed it (accidentally) remove it by
apt remove squid
If you have activated just the respective firewall macro remove it in the web GUI (<node> -> Firewall -> Remove )
Not true. You can use Proxmox firewall and any "manual" iptables setting in parallel. Proxmox is able to distinguish "manaul" and "Proxmox driven" settings from each other.
Datacenter settings are in principle nothing else than the same settings for each node (you may have in a cluster). If you...
Works if you use virtio block for the respective disk and set global parameters (example assumes that it's the third disk):
AFAICS not (according to providers how-to) - but note that it's the providers responsibility. Note that the "routed" version is a little bit tricky. Try rather use the "bridged" method https://wiki.hetzner.de/index.php/Netzkonfiguration_Debian/en#Bridged - all you need is to order an additional...
You should set lacp=active. From this apart we tested something corresponding to your configuration for a couple of days in both pve5 and pve6 and did not encounter any problems.
Note: if the switch is not configured correctly it may work for a while but sporadic blockings are possible.
AFAIU you want to move virtual disks between VMs - correct? Possible, but you have to to this by editing the corresponding .conf files. those configuration changes will have only effect after the next start of a VM from idle state. If you are not careful and assign a virtual disk to more VMs...