If the lower section can be removed (ie; it screws off) then they won't be top quality.
Cheap coilovers are often made in this fashion to enable one leg to suit a variety of different applications, not ideal. They will often loosen over time and change their adjustment. The threads often wear and/or sieze there.
Inverted shocks (ones with 40+mm shafts) are made to hold geometry better than small shafts shocks (typically 25mm shaft) Designed primarily for racing use their strength and operation are ideal for short term use, far from ideal for road use where the only lubrication they get is the initial grease from factory. Small shaft coilovers are lubed by the shock oil and are better suited to road car application where they will see many thousands of km between services (if ever)