Yes, VoLTE, WiFi-Calling and Carrier Aggregation are all supported on T-Mobile. But VoLTE on T-Mobile is having a little bit of issues and which makes the unlocked phones delayed to release an update because of that. LTE band 4 and 66 VoLTE calls will drop if you switch between these two LTE bands so T-Mobile decided to have Band 4 MFBI (multi frqequency Band Indicator) as Band 66 but Unlocked devices is not getting any Band 66 on the phone yet. Maybe next update.? T-Mobile doesn't own a lot of Band 66 licensed only on the area where they dont have B4. B4/66 have the same exact frequency just that B66 has one more block addition to their spectrum.
Currently both S10 and Note 10 supports LTE 2,4,5,12,46,48,71 by dialing *#2263#... Now, LTE-U (Unlicensed) is long gone now, it is same frequency as B46 LAA (Licensed Assisted Access) just a software update. When 5Ghz released in the USA, FCC/Network hasnt decided which LTE band to use but now they finalized and decided Band 46 LAA (5ghz) will be use in the USA for good.
LTE Band 48 (3500 Mhz) is half Licensed and half unlicensed, Although T-Mobile shows B48 on the S10 and Note 10, Tmobile hasn't deployed this yet in the USA. Verizon has been testing this B48 band since last year and I believe they are slowy rolling it out only to a very congested area. LTE Band 46 and 48 are both LTE TDD which means a one way street you can not download and upload at the same time.
Note 10 and S10 supports 7 Carrier Aggregation but T-Mobile restricts this to 3CA only and AT&T is showing 5CA support on both devices.
Video-calling may not be supported on unlocked devices. The device does support RCS for unlocked but Google is slowly rolling this out this year not yet in the USA though only in parts of the world.