you can do positional trading with options but as you pointed out theta will certainly have effect on value of option, if it is far away from expiry then there might not be much theta decay but options closer to expiry will see it a lot… your idea to buy options which are far away from expiry is good but there isn’t much liquidity and you will lose a lot in impact costs.
even options closer to expiry will give you good returns but the move in your direction should happen quickly else you will lose to theta decay, if it is late move then it has to be big move so you can make profits.
i think best way to analyse how it will work will be to analyse by plotting your position in option strategy builder, that will give you clear picture.