Is there an Apple Watch that gives me ECG capability that I can pair with an iPhone SE

Assuming your country has approved the Apple Watch ECG as a medical device

Here is a list of countries that have approved ECG

https://www.apple.com/watchos/feature-availability/#branded-ecg

Yes,here is a copy of an old ECG of mine;

Yes the Apple watch 6 has that capability,the apple watch 4 and 5 do also but they are now discontinued models and quite hard to find new.