The electronic derailleur can be lightweight if using the SRAM Red and lightweight cassette. Due to the absence of cable, your SRAM Rival is I think not heavier than the Shimano 105 of the Birdy R20 11SP.
For the brakes, TRP mechanical aren't expensive and with lightweight levers weight less than most hydraulic disc brakes excepted very high end and expensive ones.
There are lightweight removable pedals and actually, folding or removable pedals do not really reduce the folded size on the Birdy and can save a lot of weight.
For the saddle, there are comfortable carbon saddles well below 100g.