It's consistent to a point. There have been several revisions of The Hobbit and LOTR over the years, but all were done by JRR himself I believe, and were done for continuity sake and detail. As far as the worldbuilding goes, it's exceptionally consistent. Considering the bulk of all work put out was done by JRR, with Christopher Tolkien doing editing passes during compilation. For instance, the Children of Hurin and The Lay of Beren and Luthien were described in LOTR and the Silmarillion, but were not included largely due to length and incompleteness (the Silmarillion is really just a Cliff's Notes version of the full Legendarium, allegedly).

As far as a timeline goes, several are available, but I would try to steer away from most wiki sites, as they have been, in the eyes of some, 'polluted' by the handling of the IP by non-Tolkiens. (ie the movies and games like Shadow of Mordor)

Geography of Middle Earth is a somewhat complex topic, but the big deal is that it goes through some drastic changes as part of the Silmarillion called the War of Wrath. Other than that large shift, the geography is very consistent. Tolkien really, really loves his maps.

The officially published world is consistent. The Hobbit was even slight modified to be consistent with LOTR.

However, all the drafts Christopher Tolkien is using have been written at various times, they were rewritten multiple times while the overall world evolved so they are not canon or consistent.

What Christopher Tolkien is mostly doing is "adapting" these drafts into the final canon of the Silmarillion.

One nice thing is that whenever a character mentions the phase of the moon Tolkien has been careful to get the correct phase for that particular day.

The whole Hobbit business is severely out of place compared with the rest of the background. It's pastoral 18th century England in a Dark Ages setting.