Purely from a Reds psective, prefer Timu at 6 long term. Higgers is much better at the base of the scrum, and offers that really nice offload/passing game from there. Timu is a very good ball running 8 but I think Higgers has the edge at this point. Playing at 6 will teach Timu to play in that blind side channel, something he's struggling with at the moment, that long term will make him a better player.
Another thing to consider is we have St George likely coming back next week, who could probably play any position from 1 to 15, Timu being able to cover multiple positions in the back row will be very valuable to the Reds -- even just knowing what positions Timu can and cannot cover is going to be of value.
Ultimately Higginbotham is a very dynamic player, he's capable of playing anywhere in the back row, if something isn't working or there is some important advantage to re-configuring that back row he will put Timu wherever he needs to go, accordingly I expect on red zone defencive scrums to see Timu at 8 (as he'll be less of a defencive liability there and likely give more go forward).
In attack I'm almost creaming myself thinking about that nice little blind side run we'll see from Higgers picking up from the base of the scrum with Timu running that inside line to receive the offload and stomping on some poor fullback on his way to dotting the ball down under the posts!