Recently I have been seeing a wonderful evolution of Olsi from being a militarist to becoming a sound farmer.
I think Olsi is a multifunctional and multiskilled player who usually displays his brilliant farming skills in the beginning of each era. Just look at Realm 4 and Realm 2 Olsi's performance
As far as this topic of plains/plains with forests is concerned, I can tell based on my IO experience and observations that provided you have a backbone structure composed by 4 plains (in Realms 1-4) and if wood price is moderately high it is better to make other 5 provinces in plains with forests and the 10th province - boxed mountains. After all, it is only in the last 2-3 weeks of 4 months' marathon that iron price tends to considerably exceed wood price. For the first 3.5 months I have always traded wood for iron.
So as far as general plan and development strategy outlook is concerned, your 4 plains will sustain your army hiring, while your 5 plains with forests will guarantee a high level of granaries. Usually in 4 month-long realms my granary level has been 32-33. So I think if you have a population backbone consisting of 4 plains, other provinces should be plains with forests. Laesta with this province composition in Realm 4 nearly broke 1 million Networth Record in 4 months realms' history, but only unfortunate life circumstances prevented me from breaking this record.
I gave karma to That_Guy for this extremely important topic and for his calculations. They shed some light on the superiority of forests under some appropriate conditions.
