So some thoughts on this!
Most of the posters on the forum seem to be beginners or people heading up to being a a basic average surfer, some are good average surfers or average good surfers.
Why I say this is, it means they can find a board that will do everything they are capable of and then some, in off the rack boards that suit their size and weight and experience.
So CUSTOM, you go into a surf shop sales rep says "this is a custom board" my first answer is no it ain't.
Custom boards are made specifically for an individual rider who knows his stuff he goes to the shaper with whom he has a relationship, the shaper and the rider know how and what they want in his surfing so there will be tweaks to suit all the elements for that surfer's need.
A for instance, I ride a really good board length rail and everything else fit me nicely, but I believe a hardening of the concave edges would give the board more bite in bigger waves I discuss with the shaper next board has that , goes better ,advances his designs and my surfing!
A good shaper will also tell how or why an idea you have about your needs may or may not work the shaper does not wish to produce a dog board if at all possible and may even go so far as to refuse to make an extreme shape.
A genuine custom shape may be going to your factory and asking something like can you make me a board that would suit me for going to Hawaii, Indonesia or a different wave.
Once a custom board is sold on ( becomes second hand) it is no longer a custom board as it was not made for the next purchaser.
then it is a sales term only!
It is a great feeling when you believe you have progressed enough to go to your shaper and talk about what you want and go through the process with them and wait with anticipation until your new board comes home

Term custom shapes custom boards on the rack , a sales point only.
Big surf factories ( not the ones in Asia) often have a master shaper and a number of ghost shapers and a custom shape is now machine shaped to a certain level then hand finished by a ghost, then maybe a minor tweak by the master who may or may not pencil sign the blank. Equals custom shape
So a custom shape for average Joe, who comes in orders an average board but wants custom order.
Form filled out, all dimensions.
The master or a knowledgeable person checking gives delivery date and the process begins.
Machine basic shape if the board is in the standard average range final tweaks are again hand given by ghost and then finished by master and then penciled dimensions and for Joe and dated are written on the shaped blank . often this signature is the only difference.
Basic custom board little different from the other boards.
Some genuine custom differences may be in the glassing Joe selects and the fin systems.
Now a surf hero custom shape, this is a basic design that the surf hero had tweaked to their specifications! The mass aspire to surfing like hero so they buy the design and this one can be mass produced in factories in Asia and is almost exactly like the hero's board.
good or bad stuff.
If it works for you no.
The term custom is now more often than not a mere sales extra to convince someone to buy and realistically is not of great importance in benefit to ability, unless the surfer is ready to improve!
For raw beginners custom is not a need in their progress.