A fairly important piece of information omitted is what IR 27/17 actually contains. As you know, it is an index to the Death Duty registers. But this particular piece (IR 27/17) is an index to the Death Duty registers pertaining to administrations in the Prerogative Court of Canterbury.
Any search for a will is therefore futile. It is very unlikely this Henry Hughes left one, or if he did it certainly did not go to probate.
IR 27 is just an index to the Death Duty registers, and there may be additional genealogically useful information in the registers themselves. These are contained in series IR 26. To locate the entry of interest you can search the TNA catalogue, but I find it easiest to browse down to the right level.
IR 26/182 is not available online, but you could order a copy using the TNA copying service. Keep in mind that this copying service tends to be on the more expensive side, and if you have several documents you would like copies of it may be more cost effective to hire a professional researcher who regularly visits TNA to obtain the copies for you. Another option would be to order the film from FamilySearch to view at a FHC. The relevant film is 1817870.
In this particular case, if you are confident your Henry Hughes died in 1794 in Breconshire, it seems extremely unlikely his estate would be administered five years later and note he was of Glasbury, Radnorshire. Administration need not have occurred immediately after death, but in the vast majority of cases it did. I also suspect that the death duty would not have been applied to a death that occurred before 1796 even if administration was granted after that date. To be sure of this would require close inspection of the Legacy Duty Act of 1796.
If it were me, before pursuing the death duty record further I would explore the parish registers of Glasbury, Radnorshire to see if you can locate his burial and rule him in or out in this way. I'll leave it to you to decide whether this helps rule him out, but a brief search brings up a transcripion of the Glasbury parish registers which includes:
- Jan. 11. Henry Hughes, gent.
A further option is to track down other records of the administration – act book, letters, bonds – where they survive, which is easier said than done, are probably not available online, and would probably be better covered in detail in another question if you so desire. In this particular case I would recommmend going for the low hanging fruit first, so to speak.