Just a few things in no particular order.
If it's not needed, why use the feed line (length) to 'adjust' SWR or the impedance match with an antenna? There's no benefit other than it's a fairly easy 'work around' to actually tuning an antenna, and it definitely does have disadvantages. A feed line's purpose is to provide a path to get current from the transmitter to the antenna without any undue losses. Feed line length, using the feed line's velocity factor only comes into play when phasing/timing comes into play.
'Tuning' antennas is always a 'two-part' thingy involving resonant (efficient radiation) and impedance matching (SWR) which involves efficient energy transfer. If you don't do both then you have not tuned the antenna, make it compatible with the rest of the system. The 'bad' part of that is that SWR tells you absolutely nothing about resonance, and the most common way of adjusting that SWR is at the expense of resonance (adjusting antenna's length). There are several 'meters' that can tell you if an antenna is resonant but an SWR meter just isn't one of them.
'Best' antenna height. For all practical purposes there is no such thing, it always varies because of propagation (conditions). Unless you have the option of multiple antennas at multiple heights, the 'best' that you can do is to put the antenna at the highest -practical- height you can get/afford. What may work well for one particular location and propagation state may not do well at all at another location during different propagation conditions. There's no absolute, never varies, 'perfect' height for all cases. How do you tell what would be a 'best' height for your particular installation? The only sure way is by trying them all. Have fun with that! Or just take what you can get.
Chokes, baluns, line-isolators.
They all serve a purpose and are nice to have -IF- they in fact are serving a purpose. If one isn't required then it's only another 'point of loss' or possible point of failure, it just ain't doing you no good. Of those three thingys a choke is probably the least 'obtrusive/invasive/just-in-case' thingy you can use. It only adds a few feet of feed line. A choke only affects the outside of a feed line, not the inside.
A balun only makes the change from a 'balanced' state to an 'unbalanced' state. (It may do some impedance transforming, just like any transformer except it's transforming impedance.) They can certainly 'help' things, but in most cases those 'things' are specific, not just a general improvement.
Line-isolators do the same thing a choke does, 'cleans off' the outside of the feed line from the point where it's placed to the transmitter. That's what most of the 'short' radials you see on some antennas are, line-isolators.
Here's the 'disclaimer' (or the CYA thingy)!
There are gobs of things that affect how well your radio 'system' works. The above only touches on a few of them, is NOT very comprehensive or a detailed explanation, it's a 'generalized' thingy. If you want to know exactly how/why something works I would suggest hitting the library to find legitimate texts about those things, there are tons of it available.
Have fun.
- 'Doc