dnd 5e – How does metamagic adept interact with flexible casting and the sorcery points cap?

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.