windows 10 – What type of Ram module

I have an HP laptop with 8 gb ram. It’s a ryzen 5 4500u with 2 slots for 4gb ram.

I want to upgrade my ram.Laptop specs says 8gb DDR 4 3200. They gave me the following specs;

**DDR4-3200 dual-channel support DDR4-2400 dual-channel (DDR4-3200
bridge to DDR4-2666, DDR4-2666 downgrade to DDR-2400)

Supports the following.
16 GB (8 × 2)
12 GB (8 + 4)
8 × 1 or (4 × 2)
4 GB (4 × 1)

I dont understand the DDR4-3200 bridge to DDR4-2666, DDR4-2666 downgrade to DDR-2400″ What does it mean?**

I have selected a module suggested by crucial tool
Unbuffered • NON-ECC • DDR4-3200 PC4-25600 • CL=22 1.2V. will this be compatible.

Also HP says I can combine 8+4 gigs ram modules. can it be done.
Is this ram compatible. Can I mix 8+4 modules. Wil there be any slow performance.