1. Most times they are the same. Minor technicalities in any differences. Generally, the pre-refunded (aka "advanced refunding") are done at the call date, whereas the escrowed to maturity is exactly that - escrow account set up with bank, remaining principal and interest are deposited, trustee manages the disbursements...through maturity. The latter is generally done if the issue does not have a call option built in for the issuer.
2. For GO munis, you want to go to EMMA and open up the most recent certified audited financial results (CAFR). Skim through it and find the Net Position Statement (Balance Sheet). Look at the bottom line that says net position. If you see a negative or big negative number there, to make things simple, you probably just want to avoid purchasing that muni. If the net position is positive, then go to the Revenue Statement (Income Statement), go to the bottom lines and see how the fund balance has changed over the past few years. Are they drawing down year after year, or do the have positive cash flow and have increasing fund balance. Obviously we know which is better. If they are burning through cash year after year, and they have no plan or foreseeable catalyst to reverse the trend, then again, avoid.
3. Munis go on sale when rates go up. Nothing like now, but they do have their periods of volatility.
4. Since we don't know what will happen going forward, I always just buy what I'd be happy with under the current circumstances. Rates could continue higher, or the Fed could pause and then folks race to gobble up bonds sensing the next move will be lower rates. Don't overload on medium or long term issues and then you won't have to be worried about being stuck with low yielders (relative to where rates are at the moment). Nothing wrong with having medium and long term issues in your ladder, just don't overload on them...no matter how good the yields appear to be.