How could a pending I-526 impact J-1 visa?

The J-1 is a temporary visa but the EB-5 is a permanent visa. As a practical matter most F and J applicants are able to get visas but you do need to be clear (if true) that you do not plan to adjust status in the U.S. and must show your intent at the time of filing for the J-1, is not to remain permanently in the U.S.

J-1 is not a dual intent visa. Thus the application and interview must be handled carefully in order to avoid a denial of J-1 due to immigrant intent. Further, even assuming that the J-1 visa is approved and you pursue a residency training program, you will most likely be subject to a two-year-home-residency requirement or work in a medically underserved area for three years in the US prior to being able to apply for a green card. A better course of action would be to look for a Training program that allows you to do residency under the H-1B category.

It should not be a problem.

J-1s are not supposed to manifest immigrant intent, so a pending immigrant visa petition could be detrimental. I hope this helps

You need to disclose it as it indicates immigrant intent and the J-1 requires nonimmigrant intent.

If you sought to renew your J-1 abroad at American Consulate or upon inspection on reentry into the US, you could be deemed to be an intending immigrant and thus ineligible for J-1 visa or status.