Not sure what could be your problem, are both your LE device and NAS on the same net, or is there a firewall between?
I also get those two NFSv4 lines in my journal log so I don't think that's an issue.
Try rpcinfo -p 192.168.1.200 from your LE box and then see if you are able to telnet to the ports nfs, portmapper and mountd runs on.
My NFS server is a BSD variant, Xigmanas, so it probably runs a different build version of nfs than your box.
I don't really specify any options in my export file, so you could try removing yours in case there are any quirks there the server and client doesn't agree upon.
cat /etc/exports | grep Libre
/mnt/zwork/share/backups/LibreElec -maproot="nobody" -network 192.168.0.40/30
No options in my export file gives me these default options in my nfs mount on LE:
(I have async, noatime and nolock as mount options on client side)
mount | grep nfs
192.168.0.10:/mnt/zwork/share/backups/LibreElec/ on /storage/backup type nfs (rw,noatime,vers=3,rsize=131072,wsize=131072,namlen=255,hard,nolock,proto=tcp,timeo=600,retrans=2,sec=sys,mountaddr=192.168.0.10,mountvers=3,mountport=719,mountproto=udp,local_lock=all,addr=192.168.0.10)