I think I'll return to EU3, which I really enjoyed.
I loved playing as dutch minors, it was not very hard, but still challenging. I could mostly focus on trading, but usually I had to fight Burgundy, or France, depending on current geopolitical situation; it was not uncommon to see Burgundy conquering French provinces and becoming a real threat in western Europe.
If my country was relatively small, I've had better techs than France / Burgundy and I was ahead of everyone else (because I'm a rich trader!) and pretty often very high military tradition, so most of the time my army performed much better compared to theirs. It resulted in interesting wars, where I was the underdog, but with few vassals, better army, and some mercenaries, I could crush much stronger France. With war exhaustion high enough, it was possible to see France getting torn apart by freshly independent French minors. If that wasn't enough, I could always spawn some rebels by myself too! Fun.
The same scenario in EU4. France always wins over Burgundy. Always. And they do it pretty fast, so I have to hurry up and grab precious Dutch provinces before French get them. It's not wise to vassalize due to ridiculous AE penalties and artificial diplomatic relations limit, it's just easier to take territory or annex. My army is weaker than French, or on par with theirs, due to the fact that they can afford better advisers, whilst in the early game I'm too poor to hire any. French never run out of manpower, neither they have to deal with any rebels, even after long and bloody wars with Austria. I can't destabilize their country with funded rebels either. The only viable strategy for Dutch is to... ally France. At this point I can literally do whatever I want. Boring.
With the new truce mechanics it will be even harder to conquer blob countries like France or Turkey, because they'll have a lot of time to recover from a single devastating war. Unlike EU3, in EU4 bigger = better, sadly. This game has lost a lot of depth.