I just opposed France the entire game, holding the Imperial borders, making sure they absolutely never expanded east, and when i could be useful alone against them, allied and married Spain to hold them south ( and got the PU for my troubles). When i unlocked client states, I went all in on them, so 1700. I went to war with them 3 times, everytime taking all i could in provinces without going over 100% OE on my client state. Client states are your best bet for fast expansionism when coalitions don't matter anymore. For example, i created a client state on Anatolia and directly annexed the land of Egypt. Every war against the Ottos i could take nearly 200% OE. I expanded that way on Russia, France, the Balkans and in the end the Ottomans, and always expanding my client state in Italy in the meantime (I never owned land in Italy before annexing my client). I do not know how viable this strategy will be for 1.16.2, since my tech was 26/28/32
, so I would drown in corruption