Economy aside i guess you mean would rollingplains player fight better in rollingplains terrain region. If i got this right - the answer is yes, but only to some extent.
Using same rollingplains as an example - player would have some of the best cavalry - due to rollingplains economy and also improved Calvary stats - and since rollingplains is en empty field - cavalry would greatly dominate here.
Using same logic - Southmount infantry would be great at holding the chokepoints, and Wold archers would make use of dense forests for hit and run, or ambush tactics.
There are also certain home-terrain bonuses, for example, elven soldiers would slowly auto-heal and have slower fatigue drain on their home turf – which allows them to use their ability, such as hide – for much longer periods.
I can`t comment on how much of an impact this would have on gameplay - as we`d only get to work it out during the beta test.