I’m moving up the ranks of Unicorns but need TOP skunks to finish our PL quest. Is it ok to use the fully grown Golden mushroom? I haven’t decided if I just want to discard the trail after he’s been spotted twice or actually try to do our first one. Would we have enough time for the Golden to turn RFH in time. Haven’t read how TOPs work yet.

Yes, at this point the fully grown enchanted golden mushroom is fine.  And you will have plenty of time when the golden mushroom goes rfh to attract your golden uni if you do want to move on with the topiary trail. 

At this point you may as well attempt your first trail - if your first critter is the skunk, when you have completed the task the skunk sets for you, when the topiary bush is trimmed (attract 3 top skunks to your garden, spot 1 top skunk in another garden) the top plant will reset for your next task which will be grey squirrels.  Repeat process with the top squirrels.  Your third task will be for the classic unicorn.  The rfh golden mushroom will not attract a classic unicorn.  But you will have plenty of time to plant a pink cap mushroom to get it to rfh before you need to get the last top trimmed for this red trail.  Just remember when you get to the last task, do NOT dust the top bush to fully grown until you have the pink cap rfh to attract unicorns.  You can use a higher fully grown mushroom to attract unicorns like the enchanted pink mushroom, but recommended generally to use the correct rfh mushroom where you can.

If you do not diamond dust the topiary bushes between tasks you have 5 full days before the topiary is fully grown to make sure your garden is ready and set up for the next task.