but if there is 90% of hash power on one fork.. then those blocks are created at similar speeds as normal, yet the 10% hash is only making one block every couple hours for 2 weeks
if you think that it will speed up and be reasonably fast quite quickly. you would be wrong. following the 2 weeks of 1 block every couples hours it would then be 1 block every hour and xx minutes for 2 weeks, and slowly get shorter each fortnight. after about 6 months the difficulty will be low enough to be fast block creation,, but at a cost of weak security that can easily be 51% attacked.
If hash rate was 10%, then difficulty adjustment will be similarly affected. It will not happen in 2 weeks.
The first difficulty adjustment could take months to reach (4 months+? if difficulty had changed just before hard fork)
Or, if hard fork happened just before difficulty adjustment, it would then be sooner.
However, then the next difficulty will not decrease as much as it would have if it had taken the 4 months of 10% hashing power.
So then the next difficulty period will stay more difficult and will take longer to complete.
It would be nothing like ETH.
It would clearly be the losing chain.