Questions related to xlog

I have several questions in understanding xlog code:

(1)
In RecordTransactionCommit():

* (If it made no transaction-controlled XLOG entries, its XID appears
* nowhere in permanent storage

We have this in XLogInsert():

/* Insert record header */
record->xl_xid = GetCurrentTransactionIdIfAny();

So in some situations (i.e., this transaction was already assigned an
XID), XLOG_NO_TRAN entries' XID does show up in permante storage?

(2)
In smgrcreate():

* Make a non-transactional XLOG entry showing the file creation. It's
* non-transactional because we should replay it whether the transaction
* commits or not

lsn = XLogInsert(... XLOG_NO_TRAN ...);

Do we replay *all* xlogs no matter it commits or not? AFAICS, the only
usage of marking xlog non transaction-controlled is not to move
MyLastRecPtr pointer (so possiblly reduce some work at transaction
prepare/commit/abort point), and other usage?

(3)
Also in smgrcreate():

* ...; the WAL sequence will tell whether to drop the file.
*/
void
smgrcreate(SMgrRelation reln, bool isTemp, bool isRedo)

Seems nobody is reponsible to remove the smgrcreate()'d file if only
XLOG_SMGR_CREATE entry is flushed and system crash?

Regards,
Qingqing