So I wrote this up in another topic, but I basically answered my questions.
DOMAIN=192.168.1.96
docker network create -d macvlan --subnet=192.168.1.0/24 --gateway=192.168.1.1 --ip-range=192.168.1.96/27 -o parent=eth0 bridged_lan
docker run -d --network=bridged_lan --ip=192.168.1.96 -p 4443:4443 -p 443:443 -p 80:80 -v /volume1/docker/nextcloudplus :/data --name nextcloudplus ownyourbits/nextcloudpi-x86 $DOMAIN
Basically uses docker to create a virtual IP address from its internal DHCP server and a LAMP stack is created, tada! No messing around with nginx, or files, or UI.
The first thing I did with Synology was chroot it and install my normal stack, this should be the 3rd thing I do, instead of wasting time figuring out what goes where with the system.