Salaam, I do not know of systematic or institutional discrimination against Sunni Iranians, but I do not doubt the presence of micro-aggressions present at the individual level. There is a lot of room for improvement, but Iran is not Bahrain. Plus, Shia are the majority in Bahrain, whereas Sunnis are the obvious minority in Iran. From a political science perspective, you absolutely cannot compare majority and minority politics. Minorities face some levels of discrimination pretty much everywhere.
The issues in Balochistan, which is predominantly Sunni, return to the issue of ethnicity, tribal identity, and a struggle against the Persian hegemonic nationalism that became ever-prevalent post 1930s. People in Kurdistan, which ~50/50 Shi’i and Sunni, have a similar experience.
The issue of mosques is frequently brought up when talking about Muslim religious diversity in Iran. The state has a unique understanding of mosques. Their perspective is that there is no such thing as a “Shi’i mosque” or “Sunni mosque” in Iran, and practically all prayer spaces are shared.
Also, it’s important to note that for most Shi’i specific rituals, other buildings are usually used instead of mosques, such as Hosseiniyehs.
Part of this is rooted in the idea that Jafari fiqh allows only one jummah prayer in every city. In Iran, the imam of the prayer is appointed based on the majority in the city. So majority Sunni cities, especially in Balochistan or parts of Kurdistan, have Hanafi and Shafi’i imams, respectively.