I was going to say that it's quite a difficult task as it's mostly Romanian and Hungarian scholars who write about Transylvanian history and a lot of it is not in English. However, based on your post history, it seems you know both languages, so I hope I don't mind if I'll list some sources in both. I'll also try and include some in English, just in case anyone else might be interested.

However, I will say that, in my opinion, reading historical works on Transylvania can be quite a frustrating experience due to the implicit (and sometimes quite explicit) bias of many authors. A lot of scholarship in this area tends to be at least somewhat nationalistic. So, I would suggest forgetting about reading with a grain of salt and just bringing the whole bag. Also, depending on how much effort you want to put in, I'd recommend reading from multiple authors.

For general history, I'd recommend *The History of Transylvania (*the second volume is about 1541 to 1711) by Ion-Aurel Pop, Magyari András and Thomas Nägler, basically a Romanian, Szekler/Hungarian and Saxon historian from Transylvania. They also all have other publications on Transylvania if you're interested, I don't recommend Pop's more recent work as in my opinion, he has fallen down the nationalism rabbit hole. (available in English)

Miskolczy Ambrus's research focuses mainly on Transylvanian history from the perspective of Romanian-Hungarian-Saxon cohabitation and iirc, his work addresses mythos creation.

Lucian Boia is quite controversial, there's a lot of criticism towards him from other (Romanian) historians mostly for being "anti-nationalistic" as most of his work explores the mythologisation of politics, history and national consciousness and identity, and he is very critical of Romanian historiography. I personally really enjoy his work, especially History and Myth in Romanian Consciousness, it offers a really a jarring contrasts to how we were taught history in school. Afaik, he doesn't have anything specifically on Transylvania, but many of his publications touch on it and a lot of it is translated to English. Although, I wouldn't recommend it to someone as their introductory to the history of Romania.

Other authors I either haven't read or can't remember what I thought about:

Demény Lajos, mostly writes about the cultural history of Szekler people in Transylvania.

Tudor Sălăgean history and ethnography of Transylvania

Jakó Mikós, if I am not mistaken, he has some collections of primary sources on Transylvania.

This is a list of Hungarian historians from Romania, most of them probably have published something on Transylvania, if someone is looking for a more specific topic within the history of the Region.

I can't really recommend any articles, but if you prefer a shorter read, I suggest searching with more specific terms from your chosen time period in google scholar, such as Battle of Mohács (1526); Principality of Transylvania; Grand Principality of Transylvania, the Revolt of Horea, Cloșca and Crișan, etc.

Also you can search for prominent people from that time period, some that come to mind are Bethlen Gábor, Báthory Anna, Báthory Zsigmond, Gheorghe Șincai, Bolyai Farkas.

As bonus, here's a website on Transylvania's history, it's mostly shorter articles, some primary sources and relevant media content; and a book on witch trials in Transylvania.