There's some studies that show it can lower your test. I'm sure it's not to a significant degree but anything that lowers testosterone even slightly will probably be counter productive in pct. I'm not saying it doesn't work, but during pct yiur #1 priority is raising testosterone.
How much it's going to make a difference, I got no clue.
As far as ecgc increasing the oral bio of tamoxifen, that's probably ot a good idea. Tamox actually has poor bioavailabilty but it still works and has potential for a lot of side effects like most serms. By drastically increasing the bio it's probably gonna also drastically increase side effects. 2 things I'd be massively concerned about are 1. Blood clots and 2. Estrogen receptors in your eyes.