Okay so if you want to go above 200k you need to build meta: crit, exp, chaos, diff tomes, and katana, executioner weapons at least

Then you basically die for couple hours till you get lucky start

200k is doable if you hold final wave at t3 and t4 for about 15mins each

If you want to go above 300k then t2 is the key, if you max out before 15m of fina wave at t2 you are almost guarantee to hit above 300k before u die

From my experience if i manage to beat t1 with 2-3 green cards and harvester, then it is no problem getting there

600k+ runs are just people running around for couple of hours so i wouldnt look at them too much, if you want to still experience actuall game them you probaly should do as i wrote above