As I mentioned, Rav Ahron Soloveichik held that all Rishonim held the Avos (and Jews before matan Torah) had individual kedusha. However, I found one Rishon who may not agree. The Gemara (Bava Basra 58a) mentions (it's an agadata) how Rav Banah went in to Mearas Hamachpela to measure it, and he later marked off the area from the outside so Kohanim will not walk there and become tamei (from ohel hames, that a roof over the corpse transmits Tumah to everywhere under the roof). The Nemukei Yosef there (31a in Rif s.v. garsinan) quotes rishonim who learn from this Gemara that a non-Jewish corpse does emanate tumah in an ohel, because Avraham was from the Bnei Noach. From the fact the Nemukei Yosef shows that Avraham's grave transmits Tumah in spite of the fact that Avraham was a ben Noach, shows that Avraham probably didn't have any kedusha. Because they learn from Avraham that all non-Jewish corpses transmit Tumah. Unless tumah is independent of all kedusha, individual and communal, but then the last statement of the Shulchan Aruch (next paragraph) is strange.
This is a machlokes in the mishna and among the poskim. Shulchan Aruch (Yoreh Deah 372:2) says: It is proper [for a kohen] to refrain from walking on the graves of non-Jews. Rama: even though some are lenient, it is correct to be strict. And the grave of a mumar is tamei like a Jew's grave. (Note: the lenient opinion Rama brings, even though he does not accept it, argues on this Nimukei Yosef. That opinion, the Yera'im, holds a non-Jewish corpse does not transmit Tumah in an ohel, and is only forbidden for a kohen to touch it. This shita is used when a kohen wants to attend medical school - to this most lenient opinion, a kohen may be under the same roof as a corpse or cadaver, but he may not touch it.) Rav Ahron explained that a mumar, even though he loses his Jewish status, that's only kedusha of the community. But his individual sanctity remains. If so, this halacha has little in common with the first halacha mentioned - if a non-Jewish corpse transmits tumah, certainly a mumar should. Unless you'd think a mumar is worse than a non-Jew (whether because of moridim v'lo maalin or some other sevara).
A side point about a non-Jewish corpse causing tumah - Rav Yitzchok of Volozhin, the son of Rav Chaim of Volozhin, the author of Nefesh Hachaim, explained that in the mishna, Rabi Shimon Bar Yochai's opinion (Bava Metzia 114) that a non-Jewish corpse does not cause tumah is learned from a psauk "adam ki yamus ba'ohel" only tells us that a Jewish corpse causes Tumah in an ohel because only a Yisrael is called adam, emanates from the communal kedusha. The word adam is singular and plural, because the Jewish people as a whole can be considered one unit, and anyone else cannot be called adam. (See R. Joshua Hoffman's Netvort and also to Tazria 5768, but archives are unavailable for that one. Also see Tosfos, Avodah Zarah 3a s.v. Kohanim.) With this in mind, perhaps we can explain a well-known law in a new light: a non-Jew acts "for himself" according to Halacha - not just that he doesn't halachikly act on behalf of a Jew, but he only works on his own behalf, and not as part of a greater unit. (Again, I stress this is a strict Halachik framework. There are many selfless non-Jews who act for others and the public good, and some do so even at great personal risk, like Wallenberg and Schindler who saved many Jews in the Holocaust. They are michasidei Umos Haolam.) (For more on adam/haadam, see Bava Kama 38a, Yevamos 61a, Gur Aryeh Breishis 46:10.)
There is a famous book of drashos, Prashas Drachim by Rav Rozanes, also the author to Mishna Lamelech (published in the standard Rambam) who discusses whether the Avos had kedushas yisrael or were bnei Noach. He brings many midrashim back and forth, at one time bringing a medrash that Yosef felt they were Yisraelim, and his brothers felt they were Bnei Noach. It is the first and second drasha in the sefer, IIRC.