What would break first under the same load test for say a 200kg kite lines same quality etc:
20m or 30m long line?
Second question same lines but now in extreme wind remembering that there is more bend in 30m lines due to wind?
Just wondering what people think as I am now using race lines.

Its all to do with load - which is the same irrespective of the line length ! Some would argue that the longer line may have more stretch (should be 30% cuz its 30% longer ) and this might make the longer line a bit more forgiving in gusty winds.

However in term of static load - kite surfer weight eg 85 kg vs 4 x 200 kg lines = 800 kg and that's a big safety margin!!

What the point of your question ?

I hope this isn't going to turn into a parasitic drag conversation....

Just ride em and know what to do if a line breaks.

I've been using a set of 23m ozone 200/100s exclusively for foiling since about November last year, so probably approaching 100 sessions, and no sign of wear. (clouds, zeeko carbon-carver) Bought two sets of 21m for future use as they are so much better than standard weight lines with the clouds.

The thicker bottom few metres on the 200/100s is good as I loop my kites a lot. I've spun all the pigtails on my kites to knots and using all loops from the pigtails included with the race lines as thin loop to thick knot works fine but thick loop to thin knot doesn't.

I would say that these days besides damaging a line, it would only be a fault in manufacturing that would create a weak point that would cause a line break.
statisically that is probable at some point so having longer lines increases the probability of getting one of those defective bits.
i hate statistics so don't care.

I've posted this before in another thread, maybe send Gunnar a message and ask him where and why his race lines broke ?

?t=51s

I've broken race lines too. Looked fine before I went out...

Don't forget Dyneema has a low melting point -- rubbing lines weaken them and race lines don't have a lot of strength to spare.

Use race lines if you're racing and replacing them often. If you're free riding, well I wouldn't I don't think length matters.

Gunnar was riding race gear, fully powered, high speed. I believe the original poster is riding clouds, which are oriented to lower speeds and much lower power. For myself, I'm typically riding a cloud between a third and a half the size of what the racers are using. They're heeled over at massive angles putting all their bodyweight through their seat harnesses. I'm standing much closer to vertical with far less power and line tension. I also ride strapless. For all these reasons I have no fear of consequences as severe as Gunnar suffered if I break a line, and also much less chance of breaking a line in the first place. Match your lines to your individual riding style, gear choices, and acceptable risk/performance thresholds.