[OnePlus 7T Pro 5G McLaren Questions & Answers] starcms:
First, let me say,

just because the phone displays 5G doesn't mean you are actually connected to 5G. It displaying 5G means it is connected via LTE to a tower that supports 5G -- but not necessarily connected to the secondary 5G radio frequencies. The speedtest app is great, it actually shows if you are connected via 4G LTE vs real 5G.

One hint that it is actually connected to 5G is the signal strength will generally drop (from when it shows 5G but is only actually connected via LTE) and when the 5G connection is actually made. When connected to Wifi, the 5G connection is dropped and radio turned off to save power. There are two radios in our devices. The internal LTE modem in the SoC and an external 5G modem. Unlike the new OP8 phones, the OP7TProNA can only connect to 5G as a secondary connection -- it must be connected to LTE first -- always. And the data speeds from LTE and 5G cannot be combined. It's one or the other, which can present some problems (read below).

Anyway, on to my results. LTE seems more stable overall (very slightly lower ping and jitter) vs 5G. But low-band 600Mhz 5G can definitely pull in some pretty fast speeds (our phone already supports n71 (which is all that is in use for 5G currently unless you are in phili or nyc) and n41 (the coming midband 2500mhz from Sprint where the real speed will be, only in nyc and phili as of now). And with the latest update, TMobile enabled 5G support of bands n2 and n66 -- Tmobile's own mid-band frequencies currently used for LTE which will eventually be used for 5G).

Results finally? LTE more stable -- always between 40/10 and 80/12 mbps. Low Band 5G (n71, 600MHz) -- I've gotten as high as 145/25 mbps and as low as 5/5 in the exact same spot. Average around 80/15 mbps.

So it really depends on location and towers. What towers can you hit? How much have they been upgraded? The giant discrepancy in 5G speeds at my location in my case is due to phone locking onto one tower instead of a second. Both approx same distance away, same approx signal strength, both are real 5G, but 145/25mbps vs 5/5 mbps. You can see the vast difference in performance. I'm assuming one is overloaded or isn't fiber fed.

Lastly, I have not noticed ANY increased battery drain on 5G.

Low band 5G is made simply for distance while keeping LTE speeds. It's broadcast on the same 600Mhz frequency that used to be used for analog UHF TV. So it can work up to 10 miles from the tower. Eventually this will be mainly for rural areas. Midband 5G will overlap lowband 5G in cities once turned on and that's when the big increase of speed will come. But it was extremely quick and easy for them to convert almost all LTE towers into lowband 5G towers. Alot more work is required to get 5G operational on the midband.

5G service just really isn't ready for primetime yet imo because of tower issues like the one above. But your phone is ready for whenever it is (when Tmobile midband 5G goes activate across the country, probably 2021 or 2022). It now officlially supports 5G on n2, n5, n41, n66, and n71 (all low and mid band 5G frequencies that will be used in the US, you can ignore n5 unless you live in one very specific part of Florida). It doesn't support umWave, but who cares about "insane" speeds if it only works outside, while walking, while in direct line of sight of the tower. That's nothing but a gimmick. But in the next year or two while TMobile continues adding/upgrading more 5G 600Mhz towers, but more importantly starts using midband frequencies for 5G across the country, that's when the speeds will pick up...dramatically on midband. 500mbps+ easy. On the same phone. So just be patient. The phone is ready, the network not so much :)