is there a way for now to test cluster ve 4.x and ha with 2 nodes like "Two-Node High Availability Cluster" for proxmox 3.x ?
If you want reliable HA - and if you need HA you always want reliability - you need at least 3 nodes. This is true for a 2.x, 3.x and also for a 4.x HA cluster.
A two node setup is NEVER optimal and not recommended. If you have just two boxes, just run a cluster without HA.