The difference is under the hood and what apps we use and how we set up preferences within the phone.
A flagship has the features etc that a mid range phone may not have and as such can be more resource hungry.
This is where the importance of optimisation is in regards to the soc and any heat issues causing potential throttling.
I imported my N20 Ultra 5G Snapdragon version from Hong Kong which came with a 12 month warranty applied by WondaMobile and I have my phone's covered under my Home Contents Insurance.
People have got 5G working on these phone's via various workarounds.
See some relevant posts on xdadevelopers.com.
I use Google Pay personally as I prefer this method but again I've come across posts from people who imported their phone's from Hong Kong and have Samsung Pay working too.
I wouldn't import a phone from the States as these can have issues with our bands and frequencies our Network's use in the UK.
Current Phone >Samsung Z Fold³ 5G.
Previous Phone > Note 20 Ultra 5G SM-N9860.