I've been browsing through the forum in recent days while setting up a new cage for a pair of finches I plan to add to my household very soon. Thanks in large part to the valuable insight offered through this forum, many of my questions are now answered. But I thought I'd run a few of the remaining ones up the flagpole for what it's worth. Please forgive my lengthy initial post -- I promise subsequent ones will be considerably more brief!
To be honest, after devoting literally 2 entire days to researching cage lighting needs, I'm now more perplexed than ever!

BACKGROUND DETAILS
Cage size: 30" wide x 24" deep x 36" high (Avian Adventures' Loro flight cage)
Natural lighting: Very little. Cage will be approximately 18 feet from north-facing windows -- unfortunately the only windows in my condo, and the only possible spot I can place the cage without dramatically reconfiguring my home.
Species: To be determined, although I'm leaning toward Gouldians.
GENERAL QUESTIONS
1) Cage quality: I've been fairly disappointed with the quality of the cage I received. Of the 4 doors, 3 are very difficult to open & close due to apparent poor latch alignment. I noticed several very small spots where the paint does not cover the metal. Finally, half of the roof is not usable due to poorly aligned tabs. Believing it to be a mere defective product, the retailer is sending a replacement cage. But I'm concerned the real issue is a quality-of-manufacturing one (i.e. Made in China), rather than an isolated bad cage. After paying hundreds of dollars for this cage, I will be sorely ticked-off if it ends up rusting after just 6 months of use (about the time the warranty expires)! Do my concerns seem legitimate, or am I being nit-picky here? Aside from the matter of not wanting a rusty cage in a corner of my living room, does rust pose a threat to bird health?
2) Shelf: I realize that natural perches are preferable, and plan to add several. But I've also ordered a 12"-wide metal shelf. Is that too large for a cage this size?
CAGE COVER:
Due to fact the cage will be in a room where lights often will be during part of the time the birds should be sleeping, I opted to purchase a cage cover. The retailer mistakenly sent the wrong size, so there is a 1" gap between the bottom of the cover and the cage bottom. After washing the cover at some point, I suspect the gap will become even greater. Is a 1-3" uncovered gap around the cage a concern? Or is 95% coverage sufficient?
CAGE LIGHTING:
Here's where I'm in most need of help.
1) Fluorescent vs. compact fluorescent: Is there any difference in the quality of the light emitted from these 2 types of bulbs, especially from a bird's standpoint? Preferences?
2) Watts: Is a single 20-watt bulb sufficient for this size cage, or is 15-watt ok?
3) UVA/UVB: I've noticed that many full-spectrum bulbs indicate UVA/UVB output, but many do not. Should I consider any bulb without this detail, or only those that specify?
4) CRI: I'm noticing that the CRI rating varies considerably for full-spectrum bulbs. As I understand, 100 equates to natural sunlight at noon, so the closer to this the better. I've found some compact fluorescents with CRI around 91-93 and specified UVA/B, and some fluorescents with 98 CRI but they do not indicate if they emit UVA/B. Which is more important -- a bulb with a higher CRI, or one that is lower in CRI but a specified UVA/B output?
5) Night light: I'm considering a fixture with a built-in nightlight (3 blue LED lights within a single bulb). I use a nightlight in my bathroom with a single white LED light that is quite bright, so I'm wondering if the 3-LED bulb may be TOO bright, even though it is blue? Any thoughts? Are nightlights even useful at all for finches, or is night fright more a problem just for other species?
6) Placement: I'm planning to suspend the fixture from a loop inside the cage's peaked roof. This loop is 8" from the top of the cage. How much clearance do I need between the bulb and the cage top -- is 1" sufficient?
Again, very sorry to pose so many questions -- probably not the best way to introduce myself. lol I realize I'm probably over-analyzing the lighting issue, but I do want to ensure my birds get what they need.