When I export images from Lr that I'm then going to import to Id I usually use sRGB and JPEG Q80, export sharpening matt paper standard or high, depending on image. Mostly export sharpening will be high. I will then set the size to be about correct at 300 PPI for the size that I envision using it at. Most of my images stay as RAW files, that are exported from Lr only when needed, and deleted after use. Even if I do need to use Ps I normally round trip it from Lr, using ProPhotoRGB at at full native resolution. I'll then do final crop and export from Lr as with a RAW file.
I have tested the benefits of using TIFF/PSD over JPEG, and for an 8 bit file I could barely measure any deviation in pixel values between the TIFF and a Q80 JPEG. Measured deviation on any one channel is usually in the range ±2 with ±6 being a very extreme, and pretty unusual variation. In general it seems that for any randomly selected pixel the variation will only show in one channel, not all three. As I said this is barely measurable, and is most certainly not visible. If you choose to test for yourself be sure that you are comparing the JPEG to the 8 bit TIFF. For JPEG the error is at pretty much identical levels to Q80 for a Q100, you get JPEG artifacts at Q100 as well, since it uses a completely different encoding method than RGB, and conversions always have losses. In my tests there was always a bigger difference between the Q100 and Q80 JPEGs than between either of them and the TIFF.
Mostly I'm using Id to do things like business cards and advertising flyers, which usually get printed on an offset machine at a print shop. I did also at one time edit and publish the match day programs for my local non league football club (soccer for those in the US). Since given the level of attendance at games that was normally a run of only 250 copies it was cheaper to print them myself on a commercial grade laser printer on a good quality paper stock, 100 or 120 gsm it's been a few years now since I did it. In all cases my images were always done in RGB, while the Id generated elements were specified in CMYK. My output was pretty much always just a straight export to PDF, which pretty much always matched from screen to print, for both the offset printing and the Laser printer. Of course the print shop dealt with the conversion from PDF, and pretty much all inkjet/laser printers are actually RGB devices to the outside world, even if they use CMYK internally onto the paper.
Alan
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