It sounds like the question you are asking is, "what is a good small mic" and "can I get the sound I get from a 58 and external pre, from a small mic"
The short answer is, yes you can...
The long answer is, no...
When recording voice, there are a few things you can control (I will speak in general here)
Your source, voice recording starts with a human voice. All of which are different and what works for some may not work for others when it comes to mics. Lets not forget that all the vocals on Thriller were done with a SM58 and they sound great so price and quality are not always a direct relationship. Michael Jackson was a great singer and sounded great though a relatively average mic.
Your mic, you can in the end chose what ever mic you want (can afford) to record. If you go to any studio they will have a cabinet full of mics and a good engineer may have some go to's but will be able to pair people with a mic that suits them well.
A pre-amp. Do not overlook this. A $3000 mic is not even worth the box it comes in if you run it though a cheap preamp. The preamp is a large part of the sound you are getting and has a great deal of effect on it.
The ADC. There are only so many options out there in this realm but since you are using your ipad it sounds like it does not matter as I assume you are using the line in. In that case you may want to check out something like this
It will drastically improve your audio quality.
- Your consumption source. Dont forget that you can spend all kinds of fancy money on mics, pre amps and ADC/DACs but if you have bad speakers, well then your music will always sounds like its coming out of bad speakers. Since it sounds like you are on the go, get a nice set of headphones to monitor what you are doing.
On to the small mic question. I have spent a lot of time with countrymen over the years. They are my go to lav for live theater as they are skin colored, hide well, are easy to put on and sound good in a live setting. When you record them they will sound very thin, this is mainly a result of the fact that they sound that way all the time but it is less present in a large auditorium. And you can in fact adjust the distance from your mouth as they bend very easily for that reason. The countryman is not really a recording mic. And although it may be small you will need to run a pre amp that has the correct jack for it. It does not have an XLR jack as its intended to be connected to a wireless pack it has a mini jack (I cant remember the type off hand). Shure also makes some small options that I have used as over the head mics in a theater setting all sound good live but are a bit thin when recorded. I think much of this thinness has to do with the size of the element and the materials they use. Keeping all this in mind there are small mics out there, there are lots of pencil condensers that sound great and are half the size of a SM58. You may want to take a look at some of those. I have a pair of KSM127's that I use for drum overheads and other similar stuff (horns, groups of singers) and have liked their sound. You will never get Neumann U87/Neve Pre sound from a lav mic/on the go pre, its simple physics.