Hi Scatterbug. Sorry for the late reply. Been super busy with work this week. You've actually been so helpful that I probably don't need any extensive private message help now. Thankyou so much. I think the main issue I had was that i didn't actually enter the deposit as a currency but straight into USDT which is what made all the statistics wrong.
Personally I like the "Exchanged based" method because I want to have everything recorded as it actually happened in real life.
I think this is how I will prefer it. I am not too concerned with capital gains and tax calculations. I just want to see everything as in real life the same as you.
One hint I would give that could make your analysis easier: Set the purchase- and sale-values for each trade manually!
That is, when you enter a transaction then below the input field for the price is a button "Edit Asset value".
Yeah I already figured this out

Now I can focus on doing the API import. Just wondering do you use Margin trading? Not sure if the API tracks margin trades?