It is not normal to lose size after a penile implant. I highly suggest you look for another doctor. A high volume doctor like Dr. Eid or Dr. Clavell. Traveling is worth it IMO. You don't want to just go to your local doctor for such a precious procedure.
You can use VED before and after. With an LGX you may gain size after the operation.
Depending on how long you have until your operation you have a few options. The safest IMO is something like RestoreX or 8hrs of daily traction with Penimaster Pro.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4708606/If you're dangerous you can use the lghanger or the bibhanger to gain much quicker, but more dangerous. But if you're already getting an implant there's not much you can lose IMO. Just gotta keep your glans safe in which case the bibhanger is slightly preferred before an implant IMO.
In this board there was a guy who had an LGX and they used the lghanger a couple of months right before their revision. They also used VED daily and gained 4.4cm and then got a larger titan.
But I think it all starts by having an expert high-volume surgeon.