Popful Mail is one of my favorite PCE games. It's hard to believe that it was published by NEC, because it has all of the polish, extra touches and magic of a top quality Hudson adaptation like Dawn of Ys. I suspect that Falcom made this version themselves, similar to the arrangement for Legend of Xanadu.
From what I've played of the computer versions, Falcom managed to create solid and fun gameplay based around choppy movement, much more successfully than the great job they did with the Ys III. If you glance at screenshots of the computer versions, the PCE port looks extremely faithful. It does capture everything good about the original, but the in-game assets are actually mostly or completely redrawn. The new pixelart is very well done with excellent color usage and they added a massive amount of animation to the sprites.
The jump from choppy movement to 60fps transforms the visuals, but they also fine tuned the gameplay to match. If you appreciate the battlling gameplay of Ys I & II and IV, then you'll love how Popfil Mail plays. Even though the perspective is radically changed, it feels like a natural evolution from those games. It's too bad that Ys III doesn't use this formula and a PCE version of Dragon Slayer IV with the same treatment would have been a dream come true.
Although some spots can feel tedius to explore the first time through and some bosses difficult to figure out, it's still better than it tends to be in the average game from this genre. Breaking the game into stages and hubs really cuts down on time wasted travelling around.
The cinemas feature top quality art complimented by polished pixelart, vibrant coloring and an unbelievable level of professional animation for a Super CD game. It's jarring to look at the Sega/Mega-CD cinemas after you're become accustomed to the PCE version.
The Mega-CD game was very ambitious but doesn't fully realize what the developer seemed to be shooting for. Much of the background assets look cool in screenshots, but lackluster on a crt with decent image quality. It could really benefit from a color hack. The heavy use of the Sega/Mega-CD soundchip is a neat gimmick, yet disappointing compared to what an FM/PSG soundtrack could have been.
The base gameplay is fine, but feels hollow and tedius and really needed better enemy layout and stage design to compliment it. It feels like the Sega-Falcom colaboration fizzled out during the development of the game and it's a shame that they didn't begin with Ys IV.
Don't bother with the Working Designed Sega-CD version. Either play the Japanese game or the de-Irelanding hack.
If you're interested in giving the PC Engine version a try, here is an ancient version of my guide:
https://gamefaqs.gamespot.com/turbocd/563722-popful-mail-magical-fantasy-adventure/faqs