3 months after completion of tank cycling should be fine IF your params are stable. It is best if you can get a nem from local reefers. That's exactly my case and I never have any issue. I sold a split to another reefer who has a new tank. It is doing well.
For acclimation, people say only temperature acclimation is needed. I drip acclimated all my nems for 15 minutes.
In term of placement. I told my buyer to turn down his light 75% and turn off the PH. to allow the nem to settle. After an hour, he can turn on the PH but direct the flow away from the nem. He can adjust the flow after a week. He can crank up the light 5% every hour and observe. If the nem retract, then lower the light and wait a day before increasing it another 5%. It is slow adjustment, but his nem never move an inch.
My orange and white, black and white osc. didn't care for the BTA. However, when I added the maroon, it dove right in. There is a good chance your clown harem will take the BTA. Good luck.