If you use the lags, I highly recommend pre-drilling the holes full length first. I had a 36" X 96" horse barn, and 36' X 40' a shop built back in 2010 where the contractor used the Spax Power Lags. I didn't know until a month or so after they finished they split every 4 X 6 pole, by not pre-drilling. You have to remember those poles are the center cant of a log and split very easy. I emailed Spax telling them what happened and the Rep that replied asked for pictures and requested my ph.#. I sent pictures and the next day one of their engineering reps called me confirming my thought that they should have been pre-drilled. IIRC, it's even printed in the instructions on the box per the Rep. I'd already cleaned up and burned all packaging in the construction cleanup.
When I contacted the contractor about it, he offered to comeback and patch it. I was so irate, I told him I never wanted him setting foot on this place ever again, I'd fix it myself. I ended up cutting yellow pine 2 X 6's about 3' long and sandwiching that section of pole with Gr. 5, 8" galvanized bolts, then stagger spiked a 30" 2 X 4 jack stud under the headers. It's been 10 years and we've had a few decent 6" - 10"+ snows and it is still holding up well.
I'm thinking the contractor here used 5/16 X 5-1/2" or 6" lags and long enough they nearly met of bypassed each other causing the split. You're pretty much screwing a wedge in there without pre-drilling. And definitely stagger them so they are not running in the same grain of the wood.
I assume you will be using an impact driver to run the lags in. An old carpenters trick my Grandpa used, and was passed down through is to put a dab of Bee's wax on the tip of a screw, or nail for lube, and all will drive easier. A toilet bowl ring is a cheap source for Bee's wax. For screws I take a cheap ladle and bend a 90º at the cup. Cut chunks of wax, then heat with a propane torch. Then pour the wax in a empty pill bottle. I usually carry it in one side of my nail apron. For nails, all of my hammers are the Plumb fiberglass handled hammers, before that back in the early 60's we had wooden hammer handles. Simply drill a 3/8" hole, maybe 2" deep in the end of the hammer handle, and pack with the Bee's wax with your knife, or screwdriver. You may have to stop and refill it a couple times a day, but well worth it. That's a good job for a little, or big helper wanting to "help", yet stay out of the way. I know, that was my job for more than several years helping Dad when he was building something. He always had 2 hammers when building something, and it was my job to "load" the hammers and stay out of his way when not carrying materials.
