Optimal savings advice for switching to Spectrum Mobile from Verizon, while having Spectrum internet?

Currently, I pay $200ish for 2 Verizon lines, and each line has $166 remaining phone balance. I want to switch to Spectrum because it's obviously significantly cheaper. My wife and I WFH so we don't need much mobile data. Spectrum just ended my 2 year promotional discount so I'm trying to cut expenses with our 1gbps/60mbps plan, with zero other options in our area other than wireless Internet for home internet, which is not going to work for me.

I don't know if it's possible to do the phone balance buyout that Spectrum offers, to get the $166 prepaid visa cards for each phone, and then also take advantage of the $1050 trade-in promotion on the phones we have now, which just makes sense because our phones already had a huge trade-in promo and I don't mind sticking with Spectrum if they do the same thing as Verizon where these promos are paid out monthly against your bill, locking you in until it's finished. I just want to get away from Verizon.

So would it be wise to pay off the $166 each and then do a trade-in with Spectrum if we want new phones for optimal savings and value, or can we only do one or the other? I understand I have to wait months before they send the phone balance buyout prepaid cards to us. I also see that some regions require 3 lines to transfer but ours only requires 2 according to their website's offers.

I'm also wondering with the $0(1 line promo)/$30 basic mobile plans which say they stream video at 480p. What exactly does that mean? Is the mobile data connection throttled extremely hard that it can only reliably play 480p videos with mobile data? Does this throttling affect mobile data webpage loading/download speeds I assume as well?