Indeed not. The choices are between Evri and Tracked 24/48 — the Buyer chooses if they want a fast expensive service or a slower cheaper one. In my experience Tracked 48 works very well.
As for the estimations of weight/size they can work in your favour as, providing you don't over-rule the Recommendation, e-Bay will honour the price even if it's too low.
Cacas vendit.