Testabolan is not a prohormone or designer AAS. Ecdysteroids do not cause shutdown, and with how low Testabolan is dosed, you would need to be taking upwards of 10 caps a day.
Speaking of underdosed, Bold is also a very underdosed. You would need to be taking upwards of 6 per day to see full effects from it. Bold is also slow to take full effect; therefore, 4 weeks of 1,4Bold is a minimum and 6-8 weeks is optimal.
With the massive wad of cash you're about to drop on this cycle, you could just as easily obtain something more cost effective.
And now to answer your SERM question:
Clomid (which technically isn't a SERM by the way) is less toxic than Nolvadex and quicker to recooperate the HTPA. Nolvadex is better against flare-ups. It's not uncommon to use BOTH.
Such a protcol would look like this:
Week 1: 40mg tamoxifen 100mg clomiphene
Week 2: 40mg tamoxifen 50mg clomiphene
week 3: 20mg tamoxifen
week 4: 20mg tamoxifen