There are a few different types of armlocks in judo but the most popular armlock is the juji-gatame (cross armlock).

There are many different aspects to learn about juji-gatame, namely:
a) Juji-gatame roll
b) Juji-gatame finishings
c) Juji-gatame defences & escapes
d) Counters to juji-gatame defences

Juji-gatame rolls are very well-established. There are only a few proven and effective ways to roll uke over into a juji-gatame position. These are all well-known.

However, juji-gatame finishings are less established or known. The most common way to finish an armlock is to get a submission by straightening uke's arm. But there are other ways. You could switch to a hold-down or even a sankaku. You could also get a submission by inducing pain (without straightening the arm).

There are a lot of interesting variations out there but only some of which are practical. Some look good and seem somewhat plausible when done in a non-resistance context. But some of these are unlikely to work in a shiai situation where uke is trying with all his might to resist and escape.

Exotic and complex finishings generally do not work in judo where there is not a lot of time to do newaza. As such, judo moves need to be precise and efficient.

Also very seldom taught are juji-gatame defences and escapes. There are ways to prevent a roll or prevent a finishing. There are also ways to escape the juji-gatame position. But there are also counters to some of these. All of these things are not well-known and not commonly-taught. Though at KL Judo we do teach them.

None of these things are intuitive. If you want to be able to do juji-gatame well, you have to learn the technicalities and mechanics of the moves.