The Efke is a true infrared film and rated at 100 asa without a filter I have used this film with a Hoya Ir720 filter and had to rate the film at 6 asa for best results.
This film has quite fine grain for a IR film
If you expose it with a Hoya R25 (red) filter and the infrared affect is not very noticeable.
Nice film I thought good IR effect.

This film can be loaded in subdued light without risk of fogging, the film has an anti halo base, you do not get the glow that you get with Kodak HIE due to this film having no anti halo base.

SFX is a near infrared film I have only ever used this film with my Leica III with a leitz deep red filter. It worked well but not as good as a true infrared film IMHO
If you can get the maco 400 Ir film that is well worth a try as it is much faster film and you can use it handheld if you wish.