Will be interested on how you hear 'burn in' on these.

I burnt in my set with normal music listening for about 50ish hours. It did tighten and improve the bass somewhat. Did you find any significant changes with burn in?

How do the IT00 compare to TFZ Tequila 1? Do these have enough bass for bassheads?

The IT100 is much better than the TFZ Tequila1 in all departments (except bass quantity and soundstage width). IT00's bass is north of neutral but not at basshead levels. I'm a basshead and I think you might need to look elsewhere from the IT00 if u want a basshead set.

Tequila1 is a legit basshead set, but the bass is muddy and not tight, with some midbass bleed. The upper treble of the Tequila1 is darker with less clarity and details and instrument separation. Soundstage width is better on the Tequila1, but it has penalties in isolation due to the semi open backed design. Tequila1's bass is more focused at midbass, whereas the IT00's bass is linearly descending from midbass to subbass. Tequila1 is also more expensive, so not that great price to performance ratio.

it has been reported that it got a channel imbalance and driver flex on few ibasso it00 products

@Fawzay can't say for the others, but I don't have channel imbalance on mine, used my IT00 for about 100+ hours already. So far I have read in other audio forums I seen maybe 3 anecdotal reports of channel imbalance, but seems the vast majority of other users didn't report it. I guess for all CHIFI there's bound to be QC problems and outliers.

For driver flex, yes my IT00 has driver flex. Driver flex is usually due to a too tight seal, and is partially related to the tips we use and/or our ear anatomy. Seen a few users of IT00 reporting no driver flex also. As detailed above under the "BUILD/COMFORT" section, I found those methods managed to fix the driver flex for me.