Optiplex 7070 SFF Upgrade Ram

Obviously 2 sticks of 8 GB would be better than 1 stick of 16 GB to achieve dual channel performance.  You can source higher speed memory and it will run at the speed the CPU is rate for.  Compatible memory from third party is a lot cheaper than Dell memory.  See memory specs and option below.

8 GB from Dell  https://www.dell.com/en-us/shop/dell-memory-upgrade-8-gb-1rx8-ddr4-udimm-3200-mt-s/apd/ab120718/memory

8 GB from Crucial  CT8G4DFRA32A.

@Chino de Oro​

You can source higher speed memory and it will run at the speed the CPU is rate for.    See memory specs and option below.

Your screen shot shows 2666 performing at 2400 on I3 processors.

My dell spec sheet says I have a

Intel 9th Gen I7-9700 / 8 core / 12 mb cache 65w.

(intel c17,vpro,9,sml)

So how do I find out what my cpu is rated for and whether it will work at the 3200 higher speeds.

on another note, do I dare run the crucial chip (higher specd) that you provided a link for along with the lower spec dell memory chip?

thanks

Except for system with i3, all others will be running at 2666 MHz speed.

Yes, you can mixed new memory speed and it will all run at the lowest speed, 2666 MHz.