I would pick FR4 for this job. I select my FR4 Tgs by layer count not on final product environment. If this were a 1 to 6 or 8 layer board or had nice annular ring, I would go 140 Tg. It is more robust in elevated temps over long periods. Based on operating temps don't exceed 125 C. If you are doing a lot of bare board prebaking I would be cautious on surface finish selection. I am not an advocate of prebakes over two to three hours.
Boston Brad