I've been a backyard mechanic over 50 years, not a pro. I have a button that says, "I'm not old - I just have a lot of experience points". And I have a collection of tools in a carry case that's gotten heavy.
I use my socket sets with a ratcheting drive much more than combination wrenches. But I keep both, and there certainly are times when there is not enough space to get a ratchet head/socket into position and a combo wrench is needed. And I guess if you're starting out and have limited $$$ for now, combo wrenches without a socket set is a good start.
That set with the flexible box-end heads may be useful at times when you can't get a straight alignment from the side. I usually am using a socket wrench for that access problem, so I would have few occasions where I need that feature. I'm not clear whether the cost is worth it.
By "universal end" I presume you mean the ones with 12-point openings that have rounded teeth to accommodate spline and star heads. I encounter bolts or nuts like that very infrequently, so I would not buy that myself. And I agree, they would have less grip on the normal hex heads, and would be more likely to round them off. In fact, even a normal 12-point socket or box-end can round off hex heads in a high-torque situation, and for those really stubborn bolts like that I may go get a real 6-point socket.
Some of those sets have box-end opnings with a ratchet feature. That is more expensive and maybe less strong than a simple solid end. It is useful for tight spaces when you can't get a wrench into position because of angle of access. But there is a useful technique for that, especially for the open-end wrench end which makes a slight angle with the handle. Just turn the wrench over (180 degrees) and it gives you a different range of attack angles.
I'd be more inclined to get the larger plain-design set for more wrenches over a wider size range, rather than those extra-feature models. A comment pertaining to ability to deal with odd sizes. Especially on older bolts and nuts that have rusted, sometimes they seem "swollen" with rust, sometimes they actually are too small because they have lost metal due to rusting. Then thier size does NOT match the standard wrench opening. But the best way I handle that is to go the the "other" sizing system. If it's an American standard nut that is marginally too small so the wrench just starts to round it off, I switch to the Metric wrenches. There's usually one of those that falls between two American sizes. If necessary, I get one that is just marginally too small and use a hammer to tap it onto the bolt head securely before torquing on the bolt.
A suggestion for addition. I really find useful two sizes of locking pliers ("Vise Grip" or similar) I have for lots of uses. One of those is getting a good grip on worn nuts that a wrench does not grab, especially ones rounded by rusting or wear. They are also handy as a small hand-held "vise" to hold some small item I'm working on with another tool.