Hi,
you should really think about whether you need ZFS. I just reviewed my server today - i am saving ~ 25 GiB diskspace with ZFS in comparison to normal lvm-thin with ext4. I am running ~15 LXC Containers. With ZFS ~90 GiB, without ZFS ~115GiB.
Not that much... you should also know that ZFS needs much RAM and leads to higher CPU Load because of the live compression.
So i normally recommend a normal setup with ext4, if you dont want to store much data.
My way for setting up proxmox is a bit different - i am setting up a normal debian, because at this way i can create my own partition schema on the disk.
I am creating a small partition for the boot loader. The rest of the disk will be used for lvm - so i create a volume group with a 10GiB lv with ext4 for / and a 1GiB lv for /var/log. The rest of the vg will remain unused.
Then i manually setup proxmox and after that, i create a lv as a lvm-thin with the unused storage of the volume group. And this lvm-thin i register in proxmox and use it for my lxc containers.
If i am using ZFS with proxmox, then the lv with the lvm-thin will be a zfs pool. So the rootfs lv, as well as the log lv, is in each situation a normal ext4.
Thats my way to handle it - just a suggestion.
Do you store huge masses of data with e.g. much duplicate files? Then ZFS is your filesystem - otherwise you should choose lvm-thin with ext4.
I've been looking into docker as well, but I am not sure yet if I wish to use that. Seeing docker likes to mess with the firewall and is mostly only compatible with iptables, and is incompatible with ufw. Plus, the hassle of removing entire templates just for reinstallation while separating the data sounds like a pain to me.
Networking is pain in the ass with containers. But the pain with lxc aint that hard like the pain with docker. Thats why i personally hate docker. 
In my setups, the proxmox included firewall is completely turned off and im having my own big iptables script with nat and portforwarding. If you want, i can share it with you - but networking with lxc containers could be a struggle for the begin, because its a little bit difficult to understand how it works. 
But if you really want, this wont be a showstopper. Iptables is easier as it looks like. 
Hope this helps - feel free to ask if you having any other questions. 