actually, there is no such thing as agfa APX100 replacement. poetically and practically.
- i used the rollei retro 100 and it was super close (actually the same emulsion but different base etc). i dont know about the newer rollei retro 80s that appears on macodirect.de.
- acros, is a great film, probably the best modern stuff together with tmax400-2. but it is very far from the sexy look of apx100, and it is not that flexible too, u cannot really play with it. think about it as the difference between the correctness of tmax400-2 and charm of tri-x400.
- suggestions in order of appearance: (1) try the retro80s, maybe it is similar to retro100. (2) efke/adox 50, which, with some experiment will get u close. u can easily expose efke50 as 100 too. ok, maybe not exact same, but very charming. rodinal is good to start with since it worked amazing on apx100 and works equally good on efke. (3) other options are ilford fp4 and kodak plus-x... those two are not exactly agfa, but again, with some experiments u can get close. strange but on 35mm i felt that plus-x is can get a bit closer while on 120 i felt that fp4 gets closer among those two. dont know it, but i would also give a chance to efke/adox 100 as well.