Will 5G plan still work with 4G older compatible iPhone

[DelDoc]

I’d like to upgrade to for the 5G offer available today, but only have an iPhone XMax. In about 2 months I’ll have access to a 13ProMax. 
In the meantime will my XMax simply revert to 4G speeds,  but still offer the 60Gb data. I’d then like to use Speedify and my phone to stabilize my low rural hispeed connection.
I would be upgrading from the 4G 15Gb $40 plan to the 5G 60Gb $45 plan, and understand the upgrade would not affect my legacy rewards plan.
Also, I see, to recall Public having phones for sale, but don’t see any links here anymore. Is this hardware service no longer available?

Do I have all this correct?

[DelDoc]

Thanks Dunkman — much appreciated!

[Dunkman · Accepted solution]

@DelDoc 

Yes, your phone will work with 5G plan.  The major different is the throttled data speeds.  With 5G, up to 250 Mbps while with 4G, 100 Mbps.  Even a 3G customers can get 5G connection depending on location.  The speed will just be throttled differently.  

Public mobile has gotten out of the certified used phone business.  

https://www.publicmobile.ca/en/ab/get-help/articles/speed-tiers