That's the plan, like to always keep my options open on all my crews.

If you really wanted a good crew, you wouldn't consider elite gunners and elite engies...

Why is that? Because of the lower stats other then the +13's?

It's a little bit personal preference and a little bit statistical. At high levels (we're talking BB5+), a slightly higher repair stat can be helpful, as the repair cap is quite hard for most nations to reach. High level, hardcore players will therefore advocate +12s with +10 or, if you can get it, +11 repair stats over the 13/9 split you get with elites. They feel the extra repair is worth the slight weight increase for gunners and lower overheat time for engis. They don't care about the rest of the grind since they spend most of their time in BB5+. 
The only elites that gets credit from that crowd would be reps and FPs, though some will even advocate against those (restore can be of use on reps, and the same repair argument on FPs). Still, that can be a soft one that is entirely preference since fighter ability is also uncapped, meaning elites will outperform anything short of a hero with otherwise similar stats in air-to-air combat.

That being said, elites will not kill you. They will not make your crew that much worse, and anyone who says it can't be good while being elite is greatly exaggerating the disparity. It's more that you can get something that's technically slightly better in the long run without spending real mony. That said, they do help in boosting your stats during the low-to-mid levels. You'll see your shell splashes sooner with an elite BO, which is valuable on CAs and low-tier battleships, and then can keep it lighter later, allowing you to use the weight for something else, like bulge. You'll also reach the accuracy and reload caps faster with elite gunners, allowing you to shave weight off at high levels as well. Elite engis will help you reach speed caps more easily (see: Strasbourg) and give you slightly longer overheat time, which will be extremely valuable with the higher tier MN BBs, which are all run-and-gun ships. Also, for the gunners and engis, if you don't ghost them you will see a significant benefit in World At War and Axis VS Allies games where the speed and reload caps are removed.

Your crew won't be the best it can be if all elite, but it's still certainly useable, and could conceivably be better depending on your specific circumstances. Remember that despite the strong advocacy for repair, the benefit is situational. Its usefulness also depends on how and how well you play as to whether or not its worth it. If you don't often see situations where slightly better repair will make a difference, why care?


Finally, as to your original questions. MN is something of a see-saw. Once you get to the Mandel Premium CA, you will have access to the best all-around ship in its class. Period. It's often been jokingly referred the best BB2 in the game :P 
The BB1 and 2 ships often have less than stellar spread, range, and reload than contemporaries, but make up for it with higher gun counts (the Lyon and Le Havre have the highest gun count of any BB in the game). From BB3 on, you start to get somewhat better spread and reload, and faster and more agile ships, all at the expense of firepower. By the Alsace, you get both speed and firepower, which holds through BB6. You still have poor range at almost all levels and usually below-average spread as well.