build options affecting the public headers shall be set in a headers for apps.
Options such as ENABLE_AEAD_API_PREVIEW requires the app to define it whenever srt.h is included and this define is not automatically update whenever libsrt is updated/reconfigured/rebuilt.

<snip>
   SRTO_RETRANSMITALGO = 61, // An option to select packet retransmission algorithm
#ifdef ENABLE_AEAD_API_PREVIEW
   SRTO_CRYPTOMODE = 62,     // Encryption cipher mode (AES-CTR, AES-GCM, ...).
#endif
<snip>

If they are provided in a separate file, ex: srt-config.h app can also adapt their code to the lib they are building with.

#include <srt-config.h>
#include <srt.h>
...

An include for Makefiles can also be useful, to link with the libsrt configured crypto lib (--use-enclib=) for example.