How does metamagic adept interact with flexible casting and the sorcery points cap?

Question

You gain 2 sorcery points to spend on Metamagic (these points are added to any sorcery points you have from another source but can be used only on Metamagic). You regain all spent sorcery points when you finish a long rest.

Assume a level 3 variant human sorcerer has 3 sorcery points from their class and 2 from metamagic adept.

They spend 2 sorcery points from their class to make a 1rst level slot with flexible casting. Now they have 1 from their class and 2 from metamagic adept.

Are they able to convert a spell slot to sorcery points? Or can they not go over 3 sorcery points because they are level 3? In effect forcing them to spend the points from the feat before they can make more.

How does metamagic adept interact with flexible casting and the sorcery points cap?

Answer 1

You have 5 sorcery points.

It's clear from the feat that you add the SP from the feat to your current pool:

these points are added to any sorcery points you have from another source

Your maximum SP with the feat is your old max +2. Therefore, there is no reason you cannot create the 2 feat sorcery points by converting a spell slot - your max is 5.

The 2 points from the feat cannot create slots.

This is also clear from the feat. These two points can:

be used only on Metamagic.

Flexible Casting's function of creating spell slots is not metamagic, so you cannot create spell slots with the two points from the feat.

Specific Beats General

The Sorcerer's Font of Magic reads:

You can never have more sorcery points than shown on the table for your level.

Yet, metamagic adept says:

You gain 2 sorcery points to spend on Metamagic (these points are added to any sorcery points you have from another source

This is a case where we apply the specific beats general rule:

If a specific rule contradicts a general rule, the specific rule wins.

Metamagic Adept specifically isntructs us to add the SP from the feat to SP had from another source. So your maximum is definitely 5 points, and there is no reason you would have to spend the feat SP before creating new SP with spell slots via flexible casting.

You have to do some accounting.

A sorcerer with this feat creates something you have to keep track of. It creates a second type of sorcery point. Optimally, you would use the SP from the feat first, before spending your normal SP on metamagic; similarly, always create normal SP first, before creating the feat's SP.

Answer 2

The feat increases your maximum Sorcerery Points; if it didn't, the additional points would be useless for a Sorcerer

The Sorcerer's Font of Magic feature states:

[...] You can never have more sorcery points than shown on the table for your level. [...]

Meanwhile the Metamagic Adept feat states:

[...] You gain 2 sorcery points to spend on Metamagic (these points are added to any sorcery points you have from another source [...]

Clearly, the first rule simply cannot apply. If it did, a Sorcerer would never even have any Sorcerer's Points from the feat in the first place.

A level 3 Sorcerer with this feat would have not 3 Sorcerer's Points but 5 (3 from level, 2 from feat). This already violates the maximum Sorcerer's Point clause, and thus I conclude that the new maximum number of Sorcerer's Points is 5, as to have it be 3 leads to the feat's additional points being useless.

Note, these two points must be used only for Metamagic

They cannot be used with Flexible Casting or any other Sorcerer features that use Sorcerery Points.