If I am self employed which is the best subscription?

There is QB Self-Employed

https://quickbooks.grsm.io/UK-SE

But I would recommend to choose QBO Simple Start. Company doesn't provide any easier migration path yet between QBSE and QBO. We have to find yet any 3rd party tool for QBSE. Make sure you compare both edition prior to decide any of them later.

https://quickbooks.grsm.io/UK

Good luck!